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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: YoungEngineer on January 25, 2017, 04:05:20 PM

Title: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on January 25, 2017, 04:05:20 PM

This guide explains how to replace the stock Brembo rear master cylinder with a universal (Chinese) clone for a minimal cost.
The total cost of this conversion is less then the cost of replacing the seals on the stock Brembo which are now becoming very rare.

I cannot certify the quality or how long the aftermarket rear MC will last, again its a Chinese clone which is better then having no rear brakes at all (My current situation).
I would never recommend using non genuine parts for the front brakes but the rear in my opinion is not an issue due to its infrequent use.


Total cost of conversion if not using ABS is around $10-$15. If using ABS then around $25 should be expected due to the use of fitting reducers on the ABS pump.


Universal Master Cylinder


UK (http://www.ebay.co.uk/itm/142088521141?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
USA (http://www.ebay.com/itm/MOTORCYCLE-QUAD-PIT-DIRT-BIKE-ATV-REAR-FOOT-BRAKE-MASTER-CYLINDER-RESERVOIR-/172224850029?hash=item281966a86d:g:BjAAAOSw0gdXTQl6&vxp=mtr)


Thread Adapter M12x1 to M10x1 (For ABS users only)



UK (http://www.ebay.co.uk/itm/M12-x-1-male-to-m10-x-1-female-brake-pipe-hardline-in-BRASS-adaptor-HU103-/391618802491?hash=item5b2e4cb33b:g:yZsAAOSwnH1WXbXX)
USA (http://www.ebay.co.uk/itm/like/201781023214?lpid=122&chn=ps&adgroupid=13585920426&rlsatarget=pla-142405555266&adtype=pla&poi=&googleloc=1006886&device=c&campaignid=207297426&crdt=0)


Braided Brake Line (Any brake line will do over 70CM, best to find one with a 90o Right angle, I found mine used for very cheap)


UK (http://www.ebay.co.uk/itm/90cm-Gray-Motorcycle-Motorbike-Moto-ATV-Pit-Bike-Braided-Brake-Oil-Hose-Line-/131749231382?hash=item1eacddbb16:g:cMEAAOSwAuNW4piz)


Banjo Bolt M10 x 1 (ABS users only)


UK (http://www.ebay.co.uk/itm/M10-x-1-00-stainless-banjo-bolt-10mm-brake-caliper-master-cylinder-fitting-/160736873409?hash=item256caa0bc1:g:PQMAAOxy4t1Si2~F)
USA(Cannot find any on Ebay, Maybe they are called something different over there)



1. Remove rear-set, four bolts total, don't forget the brake line, the brake sensor and the reservoir tube
2. Remove the existing Brembo Master cylinder, two bolts, one is under spring tension so remember to compress the spring so that it comes out straight. 
3. Remove the existing ball-joint coupling on the inside of the brake lever using a 13mm spanner, we will no longer use it as the new MC has an internal one.
4. Remove the new master cylinder from the packaging and cut the threaded bolt in half using a hacksaw, Do not use an angle grinder as the heat will damage the seals.
5. Use a file to file down the end of the threaded bar and make sure it is smooth with no swarf.
6. Thread the bar into the threaded hole, spin the MC intil the rear holes line up and re-insert the bolts.
7. If using the an ABS system, remove the OEM steel brake line from the ABS pump, replace with a standard flexible brake line instead. You will need to now insert the M12x1 to M10x1 fitting reducer.
8. Fasten the brake hose to the ABS pump using a M10x1 Banjo bolt, fasten the other side to the rear MC using the supplied M10x1.2 banjo bolt.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on January 25, 2017, 05:21:14 PM

Thanks for the information much appreciated especially due to the cost of one in OZ. For OZ buyers it is available on AliExpress https://www.aliexpress.com/item/Audew-Universal-Rear-Motorcycle-Dirt-Pit-Bike-Hydraulic-Master-Oil-Brake-Reservoir-Cylinder-Gold/32601326433.html?
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Motorhobo on January 27, 2017, 08:39:19 AM
Someone should put this in the Lieberry. Please keep us updated if you have any issues in the future. The price of a new OEM rear MC is out of control and used isn't really much of an option.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on January 27, 2017, 08:51:39 AM
If there is more interest I may make a step by step video. However its simple enough to not need one.


I've been using this conversion for a little over a week now and it works great. The rear brake is far more responsive then the stock one, its easy to lockup the back wheel with minimal pressure.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on January 27, 2017, 10:08:58 AM
I just purchased one of these master cylinders for my K75RT.   Ever since I bought it 3 years ago the rear brake hasn't worked worth a shyt.  After buying a used cylinder, two rebuild kits and resleeving I'm done screwing around.   

It should be here in late February and I'll be reporting on how the installation goes.  I'm looking forward to seeing if I can trigger the ABS on the rear wheel on that bike.  It will be a totally new experience.   

There are a couple of things I'm curious about with this cylinder.  One of them is the long term effect of mounting the cylinder upside down with the hose to the reservoir coming in at the bottom of the cylinder.  As long as the reservoir is high above the cylinder it should be ok, but only time will tell.   Another is the linkage to the brake pedal.  I wonder what the lack of articulation there will do to side loading the seals and piston in the bore of the cylinder.   It's something I plan on looking at closely when I do the installation.

On a side note, it's disgusting the way BMW prices spares.  $255 for an assembly that I just purchased for $7 on eBay is beyond robbery.  Really, it's just a freaking die casting with a screw machine made piston and a handful of rubber and plastic bits. 
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on January 27, 2017, 10:13:53 AM
The rear brake is far more responsive then the stock one, its easy to lockup the back wheel with minimal pressure.
I'd rather have a rear brake that I can use with finesse while on a bumpy, downhill gravel road run. Touchy rear brake response isn't appealing to me under those conditions.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on January 27, 2017, 10:20:51 AM
I just purchased one of these master cylinders for my K75RT.   Ever since I bought it 3 years ago the rear brake hasn't worked worth a shyt.  After buying a used cylinder, two rebuild kits and resleeving I'm done screwing around.   

It should be here in late February and I'll be reporting on how the installation goes.  I'm looking forward to seeing if I can trigger the ABS on the rear wheel on that bike.  It will be a totally new experience.   

There are a couple of things I'm curious about with this cylinder.  One of them is the long term effect of mounting the cylinder upside down with the hose to the reservoir coming in at the bottom of the cylinder.  As long as the reservoir is high above the cylinder it should be ok, but only time will tell.   Another is the linkage to the brake pedal.  I wonder what the lack of articulation there will do to side loading the seals and piston in the bore of the cylinder.   It's something I plan on looking at closely when I do the installation.

On a side note, it's disgusting the way BMW prices spares.  $255 for an assembly that I just purchased for $7 on eBay is beyond robbery.  Really, it's just a freaking die casting with a screw machine made piston and a handful of rubber and plastic bits.


It should be easy to trigger the ABS. I replaced my rear pads as well as installed a new braided brake hose and after bleeding and bedding in the new pads (holding down the rear brake pedal at 30Mph for a few hundred feet at a time) the rear wheel will lock with minimal pressure. I think it may even be more responsive then the front brakes its quite surprising. Calipers are retracting as normal and not sticking to the disc.


As for the sideways load, this was one of my concerns however this MC is built differently to the OEM one. The stock Brembo uses a ball-joint type coupling between the pedal and the MC to provide that articulation. The universal MC has this ball joint built into it so has internal articulation providing quite a bit of movement.






Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on January 27, 2017, 10:23:30 AM
I'd rather have a rear brake that I can use with finesse while on a bumpy, downhill gravel road run. Touchy rear brake response isn't appealing to me under those conditions.


I agree, however you become very used to the new sensitivity. I can ride just fine without locking the back, but now instead of using my entire leg I just use my toes. Its just as controllable it just requires less force. Its just like riding a modern sportsbike.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on January 27, 2017, 10:24:37 AM
$255 for an assembly that I just purchased for $7 on eBay is beyond robbery. 
It doesn't approach being robbery when $7 alternatives are available. It's just plain old supply-and-demand capitalism.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on January 27, 2017, 10:29:57 AM
I can ride just fine without locking the back, but now instead of using my entire leg I just use my toes.
Great! Please continue the updates regarding the effectiveness of your modifications when you're on the 10,000 miler.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on January 27, 2017, 10:53:36 AM

Great! Please keep continue the updates regarding the effectiveness of your modifications when you're on the 10,000 miler.




Yes, well of course they may be my downfall, however in the name of science I am happy to play guinea-pig.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on January 27, 2017, 11:10:44 AM
The ball joint at the end of the piston doesn't look like it will accommodate the arc the linkage will go through on my K75.   Right now, I'm trying to find a way to allow the connection at the pedal to rotate.  I'm leaning toward a Heim joint or a threaded pin to receive the rod from the master cylinder.  Either way, it means a non reversible modification to the pedal.   

Have you been able to look at the joint on the master cylinder?  Can it be disassembled? 
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on January 27, 2017, 11:14:13 AM
Yes, well of course they may be my downfall, however in the name of science I am happy to play guinea-pig.
I'm not contending that it will be your downfall, gravity will take care of that—if you're like the rest of us. :giggles 
Your selfless dedication to science will be revered among motorcycle parts consumers and your name will be spoken with hushed awe around tire changing machines and grease barrel fires worldwide.
 :clap:
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on January 27, 2017, 11:25:23 AM
Have you been able to look at the joint on the master cylinder?  Can it be disassembled?


I've not dissembled it I'm afraid, I just made an assumption based on the free movement the threaded rod had.


I would assume the ball joint coupling is like this.


(http://www.studebaker-info.org/tech/techimages/brakesystems/55smbrapp2a.JPG)
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on January 27, 2017, 11:28:30 AM
I'm not contending that it will be your downfall, gravity will take care of that—if you're like the rest of us. :giggles 
Your selfless dedication to science will be revered among motorcycle parts consumers and your name will be spoken with hushed awe around tire changing machines and grease barrel fires worldwide.
 :clap:


lol
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on January 27, 2017, 11:34:32 AM
This is the closet looking setup I have seen. As you can see the threaded bolt has a ball-end and there is a socket/cup which would sit above the piston. So there shouldn't be any issue with side loading on the seals.


(http://www.wilwood.com/Images/MasterCylinders/MasterCylinder_Photos-Large/260-6898-lg.jpg)
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Dude on January 27, 2017, 01:34:18 PM
Nice work young Engineer.
"but the rear in my opinion is not an issue due to its infrequent use."
Mmmm,you ABS ers!
Rectify this bad habit.Best use both front and rear together.(that'll be the official line) Unless,as Laitch pointed out,your on gravel or ice and more so down hill to prevent the front wheel burying itself in a world of pain.Oh and wheelies,of course... :falldown:
Keep it coming.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on January 27, 2017, 02:23:01 PM
I have eyeballed the pedal geometry on my K75 and it looks like the end of the actuator shaft in the master cylinder will swing through an arc of at least 10mm, possibly more.  Unless there is the ability of the shaft to work over the entire diameter of the piston there will probably be some significant side loading.  It also requires a very careful setup of the pedal position to keep the arc close to centered on the end of the piston.

By allowing the pedal end to pivot, the shaft can stay centered on the piston and remove any side loading regardless of the pedal position.  That was the reason for the link which was removed to work on your bike.  That articulation at the pedal is what I hope to achieve with my installation.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on January 27, 2017, 03:08:00 PM

I'd like to see one disassembled for a couple of reasons, the articulation factor, and the piston type and location. If the type and location of the cups is the same as the OEM one, it might be possible to use the OEM housing with the Chinese piston and cylinder. I do realise that the chances are highly unlikely, but it would be nice to find a cheap source of compatible pistons and cups. The Chinese bore size is 12.87 mm one of the OEM's is 13mm a difference of .13, it might be worth a look.   I remember when it was possible to go into a clutch and brake specialist and just buy the cups. I used to race Go Karts and I bought one with a stuffed brake master cylinder. A mate bored it out and machined up a new piston and we bought new cups from a brake specialist, now no longer possible. I kitted mine not long ago, but might get a Chinese one to play with.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on January 27, 2017, 05:52:18 PM

Due to the unavailability of master cylinder kits from Beemer Boneyard and the cost of OEM kits and cylinders.  Spurred on  by the Young engineer I decided to do a bit more research. I believe that some model Ducati's and Moto Guzzi's were equipped with 13mm rear brake cylinders. There is a Ducati specialist in SO Cal  https://store.bevelheaven.com/index.php?p=home might be worth somebody local checking. I also found this on Ebay http://www.ebay.com.au/itm/New-Moto-Guzzi-Brembo-13mm-Silver-Rear-Brake-Master-Cylinder-Pump
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on January 28, 2017, 04:20:37 PM

Possible replacement for UK buyers  http://www.ebay.com.au/itm/Brembo-OE-Rear-Brake-Master-Cylinder-11mm-In-Line-Exit-Black
Performoto have heaps of Brembo master cylinders different configurations at very reasonable prices compared to OEM. Would be nice if a UK inmate could find out if they have a direct replacement and post the answer.

Business seller information

Performoto

             Contact details         



Adam Jordan
30 Gay Street
Bath
Somerset
BA1 2PA
United Kingdom

Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 10, 2017, 04:26:13 AM

I've also been looking at a couple more, hole spacing at 50mm compared to OEM 45mm, but they have the same location of the reservoir inlet between the mounting holes. http://www.ebay.com.au/itm/Rear-Brake-Master-Cylinder-Fit-Yamaha-WR250-1991-1997-YZ250WR-1990-WR500-1992-93/171911367557?   or  https://www.aliexpress.com/item/Universal-Motorcycle-Dirt-Pit-Sport-Bike-ATV-Foot-Rear-Brake-Master-Cylinder-Hydraulic-Pump-For-Kawasaki/32720693329.html?  Honda, Suzuki, Yamaha all have similar M/Cyl with the reservoir inlet between the mounting holes but the mounting holes are 50mm apart, I will do some more research before I actually order one, I'm trying to borrow an old foot peg plate and OEM M/Cyl to play with.
Regards Martin
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 10, 2017, 08:43:24 AM
I have some ideas for the originally posted master cylinder that will make for a neat, easily reversible installation if it doesn't work.   Looking forward to getting the parts that are coming on a slow boat from China.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on February 10, 2017, 09:28:49 AM
I have some ideas for the originally posted master cylinder that will make for a neat, easily reversible installation if it doesn't work.   Looking forward to getting the parts that are coming on a slow boat from China.


I don't see why everyone is so concerned about the reservoir tube being at the bottom. It works fine for me, in-fact I'm still using the original reservoir with the stock tube, its a bit of a stretch I admit.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on February 10, 2017, 09:46:19 AM
I don't see why everyone is so concerned about the reservoir tube being at the bottom.
For the record, I'm not concerned.

You're doing research that is helpful.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 10, 2017, 09:59:10 AM
I don't have a problem with the reservoir hose location.  What I am addressing is my desire to keep the original screw on the pedal and the articulated joint between the pedal and the master cylinder.

I still don't have the new cylinder so I can't say for sure, but I think I will be doing a slight modification to the mounting holes on the new cylinder, a simple bracket to allow mounting the cylinder a couple cm further from the pedal, and some way to provide a bit of a socket on the actuator shaft similar to what is on the original master cylinder to allow for some articulation.

The idea is that if, for some reason, I need to go back to original, it will be as easy as possible since I will avoid any permanent changes to the bike itself to accommodate the new master cylinder.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 10, 2017, 02:59:04 PM

I'm just trying to offer alternatives and trying to find something as close as possible to the OEM. The only problem I can see with the reservoir hose on the bottom is that it could be more vulnerable to damage and snagging.  I am waiting to see what TMG says about the articulation, as I to don't want the mod to be irreversible. The closer to OEM and the less mods the better, especially for the less mechanically inclined.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Scud on February 10, 2017, 04:15:47 PM
I bought some caliper rebuild kits from MG Cycle, because Moto Guzzi and BMW used many of the same Brembo parts - and the Moto Guzzi parts were less expensive. MG Cycle currently shows many rebuild kits and complete master cylinders available. I haven't looked into compatibility myself, but here's a link.


http://www.mgcycle.com/index.php?main_page=index&cPath=110_112

Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 10, 2017, 04:47:16 PM
I tried the local Ducati and Guzzi dealers to try and get alternate kit replacement for the OEM. They weren't interested in even looking, too much trouble to go looking, was told to go OEM. :dunno
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 10, 2017, 06:07:33 PM
The cheap master cylinder arrived today.  Haven't had much time to look at it, but at first glance it makes me wonder how BMW can justify the additional $245 for their master cylinder. 

The slotted mounting holes look like they will accommodate the spacing of the mounting bolts on the footpeg plate without modification.

The push rod pivots through something like 10-15 degrees and is solidly returned to a centered position.  The boot looks kind of cheezy, but the boot from the old master cylinder fits in it's place.

Installation will involve removing the reservoir from the new unit and connecting the hose to the hose on the original master cylinder.  Will need a hose barb and a couple clamps.

The mounting tabs are thicker than the original, so it looks like I'll need a longer screws and a pair of flat washers.

There is a tang on the end of the body that looks like it might interfere with the brake line banjo fitting.  Might have to cut it off. 

The plan for the push rod is to cut it off at about the same length as the original.  I will install one of the nuts on the push rod and will counterbore the end to form a cup for the rounded end of the rod attached to the brake pedal to ride in. 

Right now, I am not too concerned about the hose connecting to the bottom of the cylinder.  It looks like it doesn't hang down any more than the center stand.  I suppose it could get knocked off, but it would take one heck of a bump on the center stand and the rest of the stuff down there to get to it.

I hope to get some work in on it this weekend.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Filmcamera on February 10, 2017, 06:11:53 PM
Sounds good, I am watching this with great interest and look forward to your reports, as I am sure do many others, when it is done lots of photos please!
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on February 10, 2017, 06:12:26 PM
The cheap master cylinder arrived today. 
Can we please have a photo of it in its virgin state?
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 10, 2017, 07:10:15 PM
Here's a photo showing the new master cylinder with an original.  I have put the boot from the original master cylinder on the new one to see how it fits.  Looks like a good fit. 

The reservoir has been removed.  The new hose is a larger i.d. than the original.  Looks like I will need to get an adapter 1/4" to 5/16" to match them up. 

You can just see the nut on the push rod at the point where I plan on cutting it.  So far, without spending any time in the shop, I am thinking this could be as easy as the Spal fan retrofit.  Outside of cutting off the push rod and drilling a slight counterbore there is no real metalwork in this job.  Basically, it's just bolting things up.

Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on February 10, 2017, 07:18:54 PM
Here's a photo showing the new master cylinder with an original.
Thanks.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 11, 2017, 05:46:02 PM
In between painting tragkorbs and a mirror I started in on the new master cylinder.

First snag I hit was finding a reducer coupling to get from the 8mm(5/16") hose for the new to the 6mm(1/4") hose for the old so I could keep the original reservoir.  Spent two hours this morning going around to auto parts and hardware stores with no luck.  Had to order one on line for $10.  :mbird

Prepped and painted the new master cylinder black.  The gold just didn't do it for me.

Cut off the push rod to about one thread more than 1/2" extended from the body.  This puts the end of the rod about where the end of the piston on the original is.  I didn't want to mess up the geometry of the original with the pedal.

Then I drilled a 3/16" hole about 1/8" deep in the end of the rod to receive the rounded tip of the adjuster on the pedal.   The hole is to prevent the rod from sliding off the end of the adjuster when there is any side load.  The rod pivots about 10 degrees and will slide off easily with any side load on it.

Since I want to use the original boot to help hold the adjuster in the end of the push rod I cut two slots in the ribs on the master cylinder to help hold the boot in place.  When I am done mounting the cylinder and know the action is okay I'll put a black cable tie around the boot to further hold it in place.

Tomorrow I hope to get the cylinder installed and pedal adjusted.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 11, 2017, 09:33:15 PM

Looking good, looks like a pretty easy conversion could you please include pics when mounted on the foot peg plate. I looked at your conversion and was going to follow it with a few minor changes. However I borrowed a M/Cyl, pedal and plate from my mate, and at the moment I am pursuing the M/Cyl with the top reservoir mount, just to see if it is possible and what it involves. The more choices the better.If it doesn't look doable without a lot of trouble I will follow your path. How are you going to fit the hydraulic hose, new hose or an adapter.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 12, 2017, 10:12:48 AM
Martin, just fired up the heater and I'm waiting for the garage to warm up a bit this morning.  It would be nice if you guys could send a tiny bit of your heat up here, we would be glad to take it off your hands.

The hardest part so far was centering the hole in the push rod.  Fortunately, I had a centering jig to use.  Once I had a pilot hole started, I put two nuts on the shaft, locked them together and clamped my Vise Grips on them to hold the rod while I drilled the final hole.  This is a job where you definitely want to use new bits and some cutting oil.  The sharper the better.

I plan to use both the old and the new hoses.  Neither is long enough to do the job.  I have an 8mm to 6mm reducer on order to connect them.  I hope it arrives this week. 
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 12, 2017, 01:27:06 PM

OZ is in the middle of a heat wave, I'll redirect my three garage fans to blow some heat in your direction. I broke my own cardinal rule on Friday and rode back from my weekly dump day without my Kevlar jeans and jacket, rode home in shorts and a polo shirt. I think at this stage the M/Cyl that you have chosen is the better choice due to the slotted mounting holes. However I am proceeding with my choice, at this stage. However that may change today. I'm going to try and print a picture of the M/Cyl to scale if I can remember how to do it. I will definitely have to slightly slot the holes, I will probably know more by the end of the day. I was hoping to order one by Tuesday. About to go out now for my 4.30 am walk.
Regards a hot Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 12, 2017, 01:47:36 PM
Master cylinder is mounted on bike.  Took about an hour total including a bit shimming the footpeg plate out a bit to accommodate the bend that was put into it last summer when It went down on the right side.

With the 1/2" extension on the push rod the link to the pedal appears to be perfect.  Pedal action is pretty much the same as it was with the original master cylinder.  Bolting up was easy as the hole spacing and layout are nearly identical to the original.   So far I haven't even had to readjust the pedal. 

One thing, I put a dab of assembly paste in the counterbore of the push rod to insure that there will be no unusual wear there.  All that is left is to connect the hoses.  As of now I am going to use a right angle connector for the job.  Will be off this afternoon to get one and finish the job.  So far, I have only about two hours invested in this job.

So far I am very pleased at how easy and neat this is working out.  I was concerned about clearance with the center stand, but the photos show that is clearly not an issue.

 
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 12, 2017, 04:00:09 PM
DONE!!!

Jury rigged a 1/4" elbow to connect the hoses, bled, adjusted brake light switch, and the damn thing works like a champ.  Nice firm pedal with a good feel.   :clap: :2thumbup:
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 12, 2017, 04:10:57 PM

TMG I just need clarification what mods did you have to do to connect the caliper line to the M/Cyl. Pic would be nice.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 12, 2017, 06:22:52 PM

Printed out a couple of scale drawings of the intended M/Cyl with the top mount reservoir and measured everything up. While it could be possible, it would be tight due to the right angle bend for the reservoir. And due to the extra length in front of the mounting hole by the time you get it fitted no adjustment would be possible. You could make up a bracket to move the M/Cyl back enough to get the adjustment but that would require more work.
When I set out to try and do this I was after a quick cheap and simple way of doing it. As it stands Gryph's M/Cyl fulfills that criteria so I will use the same with a few mods.
Regards Martin.
Title: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Elipten on February 12, 2017, 08:11:57 PM
Hat damn!  Screw BMW and their over priced parts!


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Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Filmcamera on February 12, 2017, 08:22:09 PM
I seemed to have trouble with the link that was posted but eventually found it - at least I think I did


https://ducati-gowanloch.com/shop/brakes/brembo-ps11b-rear-brake-master-cylinder-str-black/ (https://ducati-gowanloch.com/shop/brakes/brembo-ps11b-rear-brake-master-cylinder-str-black/)





Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 12, 2017, 09:09:20 PM

Filmcamera that link was just for the rubber boot on the end of the M/Cyl. I Don't think that M/cyl will fit.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: PaulP on February 12, 2017, 10:25:21 PM
If a field-test/ report is of any use to anyone, I used one of these el-cheapo master cylinders last summer in the restoration of my K100. I'd used them before on a couple of other projects.

The original BMW one and the rear caliper had been given to a friend circa 1999, and when I looked at the price of a new one I first squinted at the screen, then I winced, followed by a sharp intake of breath, and finally a right good chuckle.

A wee bit of footering with a bracket to get it mounted (since I don't use the original footpeg mounts) and the action was champion.

I've put about 1000 miles on it now and the operation has been perfectly fine. I only really 'trail' the rear brake in either heavy stop, or complete stop scenarios, so I couldn't say that it's had much in the way of abuse, but it works as it should.

I can't really comment on the long term efficacy of the gadget, as I can't presume that it's made from highest-grade unobtanium, but it hasn't crumbled into pieces yet.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 13, 2017, 12:37:50 AM
Martin, I went to the local auto parts emporium and bought a right angle 1/4" vacuum line elbow.  The line from the old reservoir connected ok, and the 8mm line from the new master cylinder seems to work when it's clamped tight with a fuel line hose clamp.  For some reason, reducers from 5/16(8mm) to 1/4(6mm) are impossible to find, so you have to go for 1/4 to 1/4.   If worse comes to worse, and it leaks, I think I can build up the leg for the 8mm line with some marine shrink tube, the stuff with the hot melt glue inside.  Two layers should be more than enough.

The line from the master cylinder is cut to about 3 inches long.  The original line was kept at original length.  I'll post a photo of the finished installation tomorrow.

One other thing, the banjo bolt on the cheapo master cylinder is not the same thread pitch as the original, so I'm not sure how easy it would be to find replacements if you ever needed one.

The reservoir line exiting at the bottom of the cylinder makes getting all the air out a little more difficult.  Took me half an hour of tapping and working the pedal to get all the bubbles out.

Haven't had it out for a road test as it snowed today and the roads are full of salt, but the pedal has an amazing firm feel compared to the old cylinder.  It's so firm that I had to adjust the pedal slightly to get the brake light to work.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 13, 2017, 12:58:22 AM


Gryph just ordered one much the same as yours. The reservoir adapter not a problem I've got a 60 year old metal lathe and some alloy stock. Air in the system not a problem I've got a homemade vacuum bleeder made out of relish jar and a vacuum sprayer hooks to my compressor.


However I am curious on how you have connected from the master cylinder to the caliper. I've posted for help on obtaining a cheap substitute kit for the front master cylinder I've had no cooperation from Ducati or Guzzi locally thought you guys might be able to have a crack at it. Looking forward to the final pics.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 13, 2017, 01:37:31 AM
The connection to the brake line to the caliper is done with a Banjo fitting that comes with the master cylinder.  I just unbolted the line from the old cylinder and connected it to the new one.  The fitting works with the brake line, it just has a different thread pitch from the original, so they aren't interchangeable.  Or do you have the non-ABS rear brake where the line screws into the end of the master cylinder?  If you do, you will need a line with a banjo fitting if the threads on the line don't match. 

Do you have a photo of your existing master cylinder and brake line?

I used a vacuum bleeder as well, but it did not do that good of a job pulling the air out of the cylinder because of the connection being at the bottom.  Seemed that a lot of air stayed in the hose.  That's what I had to fiddle with.   The vacuum got me most of the way, but I still had to manually get a bunch of bubbles up to the reservoir. 
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 13, 2017, 02:17:11 AM

Gryph mine is non ABS, screws straight into the master cylinder. But the guy across the road operates a mobile hydraulic and brake business. But I'll wait until the master cylinder arrives in a month or two and see what I have in my box of bits. Thanks for the information now it's just a matter of waiting.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on February 15, 2017, 09:22:06 AM
Glad to see this has worked out for you. Yes the bleeding is a pain in the ass, as you say this is worsened by the inverted reservoir tube. I found that disconnecting the brake line from the caliper and sucking on it aided bleeding, but be prepared for endless jokes from passers by if doing this in a public place.


Mine to date is still working out just fine, the only issue I noticed was that my caliper was sticking, but after cleaning/greasing the pistons its now retracting correctly.




If I come up with any other El-cheapo mod's Il be sure to share them.

Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 28, 2017, 12:37:22 AM

While I'm waiting for the boat from China to arrive with the new master cylinder, decided to clean and repaint both foot peg plates. Removed  and painted the left one. While the left was drying removed the right hand one, and noticed the spring that attaches to the brake lever had gone AWOL. Had a look at my Haynes manual and it shows it attaching to a bolt with two sleeves on it. I can't find the pictured bolt and somewhere in the dark hazy recesses of my mind I think it attaches to the pin that the centre stand springs attach to. It is not a big deal as I can make something to attach it to but I might as well try to get it right. So where does it go, I had a look at Gryphs conversion but it does not show.
Regards a slightly perplexed Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 28, 2017, 12:46:15 AM
I don't have a photo, but one end of the spring connects to that flat bit connected to the threaded pushrod on the pedal. 

The other end hooks over the pin that the upper end of the two centerstand springs attach to.  There is a groove between the hooks of the big springs that the pedal return spring goes into.  The groove may be obscured by grease and muck.

Hope this makes sense.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on February 28, 2017, 01:34:26 AM

Many thanks Gryph that's what I thought. I shouldn't have looked at the Haynes which totally threw me. I've got wait till tomorrow to assemble it, paint still drying. When I get the new  cylinder I've come to the conclusion that I'll have to get a new hose, it's too much stuffing around to make an adapter. I've also decided to make a stainless steel shield to hide the hose.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on February 28, 2017, 07:46:13 AM
Martin, I wouldn't worry about hiding that hose from the reservoir.  It's not visible when you are closer than about 5 feet from the bike even when you are looking for it.  It isn't really in any danger of dragging because it is far enough inboard and the center stand protects it from bottoming out on things like curbs.

Update on my installation: 

I now have about 150 miles on the bike since installing the new master cylinder.  Rear brake works better than it ever did since I got the bike 28,000 miles ago.  It is now possible to completely stop the bike at low speed with just the rear brake which is something the bike never did before.   I don't even think about it anymore.  Operation and pedal feel is totally transparent.

So far it looks like a very well spent $20.  If I ever meet the Young Engineer I will buy him a drink, probably several.   

Screw BMW.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on February 28, 2017, 09:56:46 AM
I'm glad it worked out for you. I have also experienced good results with my setup. So far no issues on my end even with the notorious bad British weather.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: lmiklosy on March 08, 2017, 01:42:10 AM
There are on-line stores with more rebuild parts but none offer dimensional data. Here's one example: http://stores.ebay.com/ClassicCycleParts-Online/_i.html?_nkw=master+cylinder&submit=Search&LH_TitleDesc=1&_sid=24435484 (http://stores.ebay.com/ClassicCycleParts-Online/_i.html?_nkw=master+cylinder&submit=Search&LH_TitleDesc=1&_sid=24435484)   

Another: http://www.motocrossgiant.com/ProductDetails.asp?ProductCode=232%2D4153wps (http://www.motocrossgiant.com/ProductDetails.asp?ProductCode=232%2D4153wps)

The rebuild kit runs about US $90  here's one installed:  https://www.motobrick.com/index.php/topic,8790.msg68520.html#msg68520 (https://www.motobrick.com/index.php/topic,8790.msg68520.html#msg68520)
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: lmiklosy on March 08, 2017, 06:01:36 PM
 :deal:    A couple fine points.  BMW microfiche shows the MC for K75 is Magura not Brembo while BMW Boneyard explains a lack of Magura parts due to a lawsuit with BMW. I find Magura MC rebuilds in 9mm and 10.5 mm sizes but not 12, 13.   Martin reminisces over replacement piston cups in years gone by but no longer available  :dunno2:   what size are the MC bores (alternatively pistons) for those of us wishing to replace cups?  K75 microfiche specifies 12mm for ABS and 13mm for non-ABS MC bores, what are the exact measures? Somebody with a micrometer could measure their OEM part and post here for reference.   Here are usable cups on a KTM rebuild kit, piston measures 12.9mm:  http://www.ebay.com/itm/311421694121?ul_noapp=true (http://www.ebay.com/itm/311421694121?ul_noapp=true)
Getting cups off an assembled piston intact is worthy of another thread tho.   Hot water? Sauna and coconut oil?
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on March 08, 2017, 06:37:20 PM
I find Magura MC rebuilds in 9mm and 10.5 mm sizes but not 12, 13.   what size are the MC bores (alternatively pistons) for those of us wishing to replace cups? 
Max BMW (http://www.maxbmwmotorcycles.com/fiche/DiagramsMain.aspx?vid=51745&rnd=12082016) has Magura rebuild kits for 12mm and 13mm.

Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: lmiklosy on March 08, 2017, 07:55:58 PM
Ariete is an Italian manufacturer of motorcycle plastic bits, heed their warning (http://www.ebay.com/itm/Grimeca-12mm-diameter-brake-master-cylinder-052-059-seal-kit-4807069844-12868-/171974985769?hash=item280a820829:g:sI0AAOSwI-BWJw93&vxp=mtr) "Don't use Chinese junk on your classic bike"  :nono
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on March 09, 2017, 03:00:51 PM
The Chinese would have to lower the bar an awful lot to be as bad as the stupidly priced BMW/Magura master cylinders and rebuild kits I have had to deal with.

At least with the Chinese stuff I'm not grossly overpaying for what I get.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 09, 2017, 10:12:24 PM

Received my master cylinder on Wednesday full price including the slow boat from China $14.00 Au, which means I can buy 21.42 Chinese ones to one OEM one. A friend of a friend made me up a new hose for the exorbitant price of $10.00 in stainless braid.  He also threw in a new rubber boot to go over the end of the cylinder and is going to put me onto a local source for  boots and cups. I bought a new 8mm x 1.25 bolt to replace the OEM brake pedal stop which I will machine a recess into the head in order to keep the brake cylinder rod from moving off the stop. While I am at it I will make a reducer to go between the OEM reservoir hose and the new reservoir hose. I will keep and store my OEM hose and and still functioning cylinder as a spare. I will post pictures of the conversion when I am finished. With the savings of $276.00 I am wondering how many profiteroles I can buy.  :lets-eat:
Regards Martin
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Elipten on March 09, 2017, 10:21:18 PM
Martin

Keep a drawing with the dimensions that way others can get their parts machined.


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Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 09, 2017, 10:29:13 PM

I am just machining them because I can, you could do the same thing with a drill press. It is just the reverse of what Gryph did, he put a recess in the end of the push rod. But I will take photos of the process, however my lathe is old and very sensitive and it does not tolerate being laughed  at. I think it was once owned by Noah.  :dunno
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on March 09, 2017, 11:06:41 PM
Martin, I didn't even use a drill press.  I clamped the master cylinder's threaded rod in a pair of vise grips which I then clamped in the vise on my carpenter's workbench(I'm a woodworker, not a machinist) and went at it with a portable electric drill.  The fanciest thing I used was a center guide from QuikCenter to help center the pilot hole in the end of the threaded rod.

Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 10, 2017, 01:46:23 AM

Gryph I was lucky about 30 years ago I picked up my lathe from a Harley workshop that had gone broke for $300.00. Made back the $300.00 the next week making stub axles for the local Go Kart hire business run by a mate.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 10, 2017, 02:45:16 AM

Elipten as requested a variation on Gryphs method. I cut down the master cylinder pushrod shaft so that 8 mm showing after the nut and carefully removed two threads with a pencil burr grinder. The new stop bolt was cut down to 30 mm, the head thickness was 5.2 mm and the recess was cut in 3 mm. The thin lock nut for the stop bolt was salvaged of the new pushrod shaft. The whole thing was then mounted on to a spare foot peg plate that I borrowed of a mate. When I mount it on the bike I will use flat and spring washer and paint it black. I'll also put on the master cylinder boot I scored over the new boot. Apparently the OEM reservoir hose diameter is different than the new one so a reducer will have to be found or made, Gryph came up with a solution for that problem. If I can't buy one I'll probably make one from aluminium stock in the lathe. Link for 6mm to 8mm barb reducer  http://www.ebay.com.au/itm/Plastic-Barbed-Connector-Pipe-Hose-Joiner-Tubing-Fittings-Air-Fuel-Water-Petrol-/ The new hose total length is 300mm, the guy that made it has contacts for master cylinder cups and boots so I'll definitely be giving him another visit.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Elipten on March 10, 2017, 07:05:42 AM
Thanks Martin.  I am sure others will find this helpful


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Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on March 10, 2017, 09:35:14 AM
Nice job Martin!  I had the opportunity to buy an Atlas Lathe at a garage sale for $100 about 40 years ago, but at the time I was living in an apartment.  I still regret not being able to get it. 

Are you going to put a boot over the joint between the master cylinder rod and the push rod on the pedal?  I wanted to keep as much dirt and water out of the contact area as possible to protect the lube that I had put on the contact point between the two rods.  The stock boot works pretty well for that.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 10, 2017, 02:27:20 PM

Gryph the OEM  boot won't work with my mod, but the one I got given might. I am going to see the hose guy again Monday or Tuesday and find out exactly where the mob that supplies boots and cups are located. I am also going to chase up a local supplier of the 6mm to 8mm barb hose reducers, although as I posted they can be had online for under $5.00. Today I am heading up in them thar hills to a motorcycle swap meet at Maleny yee har. Was going to go up in my mates ute due to the fact he still hasn't got one of the herd going. But I am now going to ride up due to the fact my lovely wife has decided to share her cold with me. I will post more on this as I get more information. And a thank you to the Young Engineer for the idea, if he's ever in OZ I will bake him a Koala pie. :riding:
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: lmiklosy on March 10, 2017, 03:45:26 PM
This might be the Magura repair kit (http://www.magura.com/en/components/powersports/originalspareparts/productdetailpage/?p=21710) for a K75S (ABS 12mm non 13mm) but the page won't display.  :nono Magura isn't talkin'.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on March 10, 2017, 03:56:37 PM
From now on rebuild is not an option for my rear master cylinders.  For $12 and two hours in the garage I can't even start to waste my time thinking about BMW or Magura.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 10, 2017, 04:06:26 PM

Same here I won't bother with OEM will only keep it as a spare. But in saying that might just order another Chinese one to keep in stock. I did research the Chinese ones and couldn't find anything negative other than sight glass failures, and seeing as we don't have a sight glass I'm not worried.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on March 10, 2017, 04:26:19 PM
A master cylinder is not rocket science.  A couple aluminum alloy die castings, a few screw machine parts and some rubber bits.  Could be made in the USA for 25-30 bucks. 

$255 is beyond delusional.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 11, 2017, 04:22:20 AM

I used to race Go Karts and have made master cylinders from scratch as Gryph stated we are not dealing with rocket science. I had an epic fail today machining up the 6mm to 8mm reducer, on the last bit the tool caught and it tore itself apart. Two hours down the drain will try again tomorrow with a smaller bore size.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: wmax351 on March 11, 2017, 11:06:28 AM
This might be the Magura repair kit for a K75S (ABS 12mm non 13mm) but the page won't display.  :nono Magura isn't talkin'.

Good find.



http://webcache.googleusercontent.com/search?q=cache:aod0tXf829wJ:www.magura.com/en/components/powersports/originalspareparts/productdetailpage/%3Fp%3D21710+&cd=1&hl=en&ct=clnk&gl=us

Try google's cache.

Here's a place to order it. https://www.louis.eu/artikel/magura-repair-set-for-bmw-288-brake-lever-assembly/10019379
Looks like the part is a magura 288 master cylinder. Rebuild kit is (I Think) magura part 10019379. That might be the part for the louis cycles, though.

(http://www.britishdealernews.co.uk/sites/default/files/Magura%20Repair%20Kit_web_0.jpg)



https://cdn1.louis.de/content/catalogue/articles/zusatz/anl/10019379_MAGURA_Anleitung.pdf?_ga=1.50803680.873073721.1489248398


Here's the manual to install.


Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on March 11, 2017, 11:17:58 AM
Good find.
Here's the manual to install.
I just used that site to find a dealer, not that I need these components. The only dealer was Onion River Sports—a high quality outdoor gear dealer in Montpelier VT whose motto is Muscles, Not Motors. They must be supplying disc brake components made by Magura for bicycles.



Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: lmiklosy on March 11, 2017, 01:45:49 PM
Didn't mean to mislead anybody, as wmax351 found the Magura Repair-Kit does not fit the K75S, see the applicability under TECHNISCHE DETAILS on the Google Cache page. With no test history the Chinese replacement MC is unknown but I'm happy to begin testing, mine is on the way from Zhejang.  For those who wish to rebuild cylinders with new parts I'll report back with any sources I find. As a matter of fact a variation of the EPDM rubber used for MC plastic bits is used in the thermal liner for US fleet ballistic missiles and the NASA Space Shuttle, Ariete (http://www.ebay.com/itm/171974985769?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT) offers those bits. The material science it would appear supports rocket science.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: milq on March 11, 2017, 07:56:14 PM
Good stuff! I've used a very similar MC as well as a caliper to rebuild the rear brake system on my son's Yammy Blaster a couple years back. Everything worked well and just required a couple of brackets that I made in the shop.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 12, 2017, 01:07:28 AM

Made up the 6mm to 8mm adapter learnt by my mistake on the first one. Placed the adapter behind the foot peg plate, I ended up cutting 25mm of the OEM reservoir line and cut the new hose down so that it curved up to meet the OEM line. I was expecting problems with the bleeding but my home made Nescafe bleeder coped well. As I pushed down on the pedal with the bleed nipple open and connected to the bleed jar, I pulled the trigger on the suction gun, I kept doing this until no air was being drawn out of the caliper , it did take a little bit longer than usual. I am happy with the ease of the conversion and it doesn't even look dodgey looks pretty much OEM. Not to sure if I could of shortened the hose to the caliper but I think I'll leave it. I put the boot on that I scored for nothing, I could have put the OEM boot on with a slight modification but I am going to try and track down the supplier of boots and M/Cyl cups. I put a dab of marine grease on the end of the stop where it meets the push rod.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on March 12, 2017, 01:23:30 AM
Looks pretty nice, Martin.   :clap:
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 12, 2017, 01:39:50 AM

Thanks Gryph I'm very happy with it. However all up it took about 5-6 hours to make the two reducers.  :dunno  The first one sheered just as I was finishing the last couple of passes, the centre hole made it too weak. The second one I just drilled a 3mm pilot hole through it which when I tried to drill it bigger the bit jammed could not free it up. I eventually broke off the bit, the only way I could eventually get it out was to cut off the lump at the end and drive it out with more 3mm drill bits. At $50.00 and hour that means it cost $250.00.
I don't think I'll get a job making 6mm to 8mm adapters.  :hehehe :hehehe
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on March 12, 2017, 08:56:53 AM
Hey, $250 is the same price as a rear master cylinder.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: wmax351 on March 12, 2017, 10:14:35 AM
It would be helpful if someone with the master cylinder disassembled could measure the cup seals and all other associated parts, front and rear. Trying to find an alternate source of these would be excellent. I can talk to some engineering friends about where to source them.

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Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 12, 2017, 06:36:22 PM

Gryph master cylinders in OZ are $300.00 so I saved $50.00. :hehehe If I'd been patient I could have ordered one of EBay for $5.00. :dunno  Max I am going out today to see if I can find the local supplier of cups and boots. I don't think finding a supplier of cups and boots is a problem, the problem is fitting them. As previously posted a special tool that slides over the piston and is tapered allowing the cup to be slid up and into the groove needs to be made or sourced. With the supply of rear master cylinders now solved for some of us, I am now just trying to solve the front master cylinder problem. I have thought about making a tool for the front cylinder cup replacement, but I need measurements, piston diameter and how far the tool needs to slide onto the piston. The other problem is a source of material for the tool, I have aluminium but I think polished stainless steel may be better. I am going to talk to a mate who has lathe tools capable of cutting stainless steel and might have a scrap piece to work with.
Regards Martin.

Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on March 12, 2017, 06:57:58 PM
Martin, If  I recall, the tools I remember were machined out of aluminum or brass.  I think the tool needs to be softer than the aluminum of the piston you are putting the seal on.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 12, 2017, 10:57:55 PM

Just got back from chasing up a cup and boot supplier. I a good talk to Glen the guy that owns the business, he seems to be one of two places in OZ the other is in Adelaide SA. He is a really nice guy and was very helpful. He sleeves the old cylinders in imperial stainless and the OEM pistons do not fit, so he makes new pistons out of brass. He does not like doing the rear OEM cylinders as the plastic piece for the reservoir is extremely hard to get out and it invariably breaks he then has to make a new one out of brass with an "O" ring   seal. He was reluctant to give a price on doing these and when I told him about the Chinese ones he said good. Cylinder sleeving costs $200.00 and under a two week turn around he gets cylinders from all over and will ship. He does guarantee and test them, but you need to tell him if they are not going to be used. Because if left sitting the brake fluid dries out and forms crystals which will cause the cylinder to leak. Replacement cups for his cylinders are $10.00 replacement boots are $4.00 picture attached. I asked him about the special tool to get the cups back on to the pistons. What he uses is a couple of well linished screw drivers with no sharp edges and plenty of rubber grease. I also dropped in on a mate and he is willing to make up a special tool out of stainless if needs be, if I can supply the measurements. I also got a bit more aluminium stock but I am concerned about the wall thickness required when placed over the piston. Before I can proceed I need someone to supply accurate measurements of the front master cylinder piston.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on March 13, 2017, 01:03:46 AM
Does your buddy have a replacement for that friggin' clutch boot that tears if you let the arm slip and costs $40(probably $70 next year)? 
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 13, 2017, 03:51:54 AM

Good question Gryph, I will see if my mate has an old one to do a comparison. If not do you have the measurements. If they can be had cheap I will post you one or two.They used to be $20.00 on EBay, just had a look, now $30.00. The EBay guy is sort of local south of Brisbane. I thought $4.00 was pretty reasonable for the master cylinder boot so I bought two. Apparently my boot never went over the brake pedal stop as yours did, I will rectify that situation with one of the new boots. I know you had a bad experience with sleeving but after talking to this guy and his very reasonable pricing I would give it a go if needed.
Regards a satisfied  Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: wmax351 on March 13, 2017, 10:14:40 AM
Does your buddy have a replacement for that friggin' clutch boot that tears if you let the arm slip and costs $40(probably $70 next year)?


You can do some searching, you might be able to find something. But I doubt it will save that much. BMW parts, as expensive as they are, are not that bad on the scale of things: They are also readily available. Try getting some rubber stuff for a honda from the 80s.

If you get the dimensions, you could look here.

This is just a random small one I found. http://www.rubberstore.com/catalog/neoprene-multi-convoluted-rubber-bellow-20mm-connector-p-8054.html (http://www.rubberstore.com/catalog/neoprene-multi-convoluted-rubber-bellow-20mm-connector-p-8054.html)


Or just get one here: 29 bucks. http://www.boxer2valve.com/motorcycle/2313731.html
Seems like they sourced one somewhere. Cheaper if you buy in bulk, so they might have ordered a few dozen.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 25, 2017, 07:47:00 PM

Finally fitted the new $4.00 boot. I had to relocate the brake pedal stop bolt lock nut to the back of the pedal, this required grinding a bit of the pedal to allow the nut to rotate. I can live with that as I can still go back to OEM even with this modification. I also had to cut a slot in the end of the bolt to allow adjustment with a screwdriver. This boot now totally seals it against road scum and water ingress. Instead of using a cable tie I found a non worm drive S/S hose clamp of the correct diameter and I also painted the reservoir hose clip black. My Brick owning mate, originally did not like the thought of modifying the Brick with a Chinese master cylinder. However after seeing the ease of the modifications, has now got me to order two for him. So I have placed an order for three, two for him and one that I might pull apart and have a look at or just put into stock. It has now been on the road for a while and I don't have any problems with tendencies to lock up it does however present a firmer pedal compared to the OEM.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on March 27, 2017, 11:58:11 PM

Received the three Chinese master cylinders today cost $40.00 AU for three or $13.33 Au each. To pull them apart you need push the boot off the nut and screw the nut up out of the way, then gently pull the boot out of the recess in the master cylinder, it is just pushed in and does not sit in a groove. Next using circlip  pliers remove the circlip. The piston is then free to be removed. Looked at the bore and it looked fine no imperfections, the piston also looked well made. A set of cups locally for the Chinese one $10.00 AU, but not worth the trouble.


The second picture shows the OEM piston below the Chinese one, the Chinese piston is larger than the OEM one, and therefore unless you want to rebore the OEM cylinder and try and line up the ports is not a substitute kit. But who would want to do that anyway, with the ease and cost of the Chinese replacement.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: arnonymous on October 29, 2017, 02:52:43 PM
Soooo, after discovering this thread, i thought i'd try the same with my leaky rear master cylinder.
I got the same chinese cylinder, and proceeded with the first approach as YoungEngineer shows in the OP. But i noticed that the brake wouldn't move smoothly due to the excessive sideloading, it just didn't feel good, and wouldn't push deep enough.
So today i cut the shaft shorter following Gryphon's approach, drilled a "cup" into it and using the original ball-end push-rod on the brake lever, the whole thing just moved smoothly :clap: [size=78%].[/size]
I then tried to refill and bleed the system, but for some reason this is where i failed.
I have (K75RT) ABS, and the original FAG banjo(quite fat one) coming from the ABS pump seems to fit the new MC, only with the new bolt, as others described.
To remove air from the reservoir hose, i used pliers until no bubbles come out of the reservoir.
I then used my normal bleeding procedure, without a vacuum, which always went quite fast for me. Now, though, nothing happened so i connected a vacuum, but no matter how much i pump on the brake lever and the vacuum,  i can't get the brake fluid moving... the level in the reservoir never drops. Does this mean i just have an air bubble at the MC entrance?


Any tips on getting the system pressurized, why is this failing?!?


ps. Quite disappointed to discover,  the ABS system passes the startup test with and unpressurized system. Apparently it just tests the brake light switch.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on October 29, 2017, 03:16:20 PM
You are quite right about following Gryphon's  approach. I soon followed as I noticed the brake sticking on. I've not had any problems since. It may be worth updating my original post.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on October 29, 2017, 03:25:01 PM
I assume you are opening the bleeder at the input to the ABS modulator, is that correct? 

Are you getting anything coming out of the bleeder?  Do you see air bubbles coming from the bleeder when the vacuum is applied?

Is the pedal allowing the rod on the master cylinder to fully extend?  This is important because the orifice that allows fluid into the cylinder only opens at almost full extension of the rod.

I had used a vacuum pump to bleed my brakes in the past, but stopped because it seemed to suck air into the system at the master cylinder because the orifice to the reservoir was so small in the master cylinder. 

I would suggest cracking the bolt on the banjo fitting on the master cylinder and trying to bleed by pumping the pedal until you see fluid coming out, then go to the ABS module input connection and do the same, followed by the ABS module bleeder. 

As far as ABS self test, I think all that is checked is the brain, power(12v), that the wheel sensors both work and register the wheel speed, and that the motors in the modulators are connected.  The other test when pulling the brakes is for the brake light bulb monitor and the brakes switches.  That test is not part of the ABS startup and is also found on non-ABS bikes.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: lmiklosy on October 29, 2017, 04:30:29 PM
Everything Mighty Gryphon said but I'll stress two points.

First if the brake pedal adjusting screw is tightened against the master cylinder plunger too far, the fluid supply hole will be blocked and no brake fluid can enter the master cylinder from the reservoir to displace the air.  Second, as you pump the brake pedal the MC piston does not sweep the entire volume of the MC. If there is an air bubble in there it will remain there laughing at you whilst you pump away at the brake.  :hehehe To help rid the MC of bubbles loosen the banjo bolt on the MC outlet side and work the break pedal again, you will see bubbles leave the system at the banjo bolt.  Tighten the bolt and move downstream to the next fitting (ABS pump if so equipped). The ABS pump has a bleeding fitting, connect a clear vinyl hose there and repeat pump the brake pedal. Watch for air bubbles leaving the system in the hose.

Hope that helps.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Andrew2 on October 29, 2017, 06:26:39 PM
You are quite right about following Gryphon's  approach. I soon followed as I noticed the brake sticking on. I've not had any problems since. It may be worth updating my original post.


 Hey YoungEngineer, thanks for starting this thread, it's been invaluable :2thumbup: .


  Cheers
  Andrew
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: arnonymous on October 29, 2017, 07:30:13 PM
Thanks for the replies, it does seem to make most sense that its probably set too tight, and basically never fully retracts to allow fluid in.
I'll try again, and report soon.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: YoungEngineer on October 29, 2017, 08:02:31 PM

 Hey YoungEngineer, thanks for starting this thread, it's been invaluable :2thumbup: .


  Cheers
  Andrew




Not a problem.at all. I'm glad that it's been useful to others. I will amend my post at some point to make sure new viewers do not make the same mistake I did.


It's quite obvious now why BMW engineers put that pivot point in where they did.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: jdaley on January 30, 2019, 06:46:01 PM
Thanks for this onfo, its gr8. I am building a K100 into a racing sidecar
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: lmiklosy on January 30, 2019, 07:21:00 PM
Rear MC rebuild update:    I rebuilt my MC using a piece of tough silicone rubber brakeline.  Slid the brakeline on a mandrel chucked in a drill, sanded the contour to a piston seal shape and installed the seal on the piston with some Brembo silicone grease.   This fix cost $0 and works, no leaks since 2017.   My Chinese brake cylinder remains in a box  as a spare.    :twothumbsupp
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on March 10, 2019, 05:07:08 PM
Update as of March 10, 2019:

I have now done the retrofit on a total of four bricks.  Two 1994 K75's with ABS and two K100RS 16V. 

First off, there appears to be two ways the rear brake line is attached to the master cylinder.  Either with a banjo fitting or by screwing a threaded hose end fitting into the end of the master cylinder.  The banjo fitting is the easiest, just use the bolt that comes with the new master cylinder.

The brake line that screws into the end of the master cylinder will raise problems as the Chinese master cylinder has a different thread.  In order to connect the rear brake line you need to get a new one with a banjo fitting so you can use the bolt and washers that come with the new master cylinder.  Another option(that I haven't tried) is to have a new hose made with a fitting with the correct thread.  Either way, you need a new brake line.  If the existing line is original, you probably need a new one anyway.  Even if you are replacing a newer line, you are still ahead of the game with the money you save with the Chinese master cylinder.

Second, Instead of trying to splice the new supply line to the old one, I just go to the auto parts store and buy 3 feet of rubber vacuum line.  A couple inches of 1/4" i.d. clear vinyl tubing from the hardware store is also needed.  Total cost should be under $3.

Take the fabric covered hose off the bike's reservoir.  You need to open the clamp to do it.  Be careful not to break the hose barb on the reservoir.  Push the 1/4" vinyl tube onto the barb, and cut it off even with the end of the barb.  Spread a small drop of liquid  soap on the tube, and push the 5/16" vacuum line over it.  With the tube and hose I get, the fit is so tight no clamp is necessary to hold it together.  Feed the hose down and connect it to the new master cylinder using the clamp that came with the cylinder.

The bonus here is that the 5/16" vacuum line allows the fluid to flow more easily to the master cylinder, making the bleeding and flushing of the rear brake incredibly easy compared to doing it with the old 6mm OEM line.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on August 18, 2019, 09:05:02 PM
Master cylinder update, over two years on Chinese master cylinder with no problems. I had one as a backup but I kept of having to sell them.  One was mate of a mate and has not reported any problems with his after a year of use. I just ordered another spare $14.05 Au slightly up in price from $13.33Au. However this time I used a different supplier and it comes in black so worth the extra .72 cents. I would never bother going back to an OEM cylinder or a kit. It's a lot easier and quicker to just replace it with another Chicom one.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: lmiklosy on August 19, 2019, 12:37:08 AM
Same here, piston seal fix still holding no worries. Spare Chinese MC remains in box.   :bmwsmile
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on August 19, 2019, 07:13:43 AM
I've installed them on four bikes now.  Total mileage on the master cylinders is over 20,000 miles with no problems.  The modifications necessary to install them are fairly straightforward to me now and are easier than doing a rebuild(and with a lot better results).

The only thing you need to be careful of is the brake line fitting on the cylinder.  Some of our bikes have the line attached with a banjo fitting, and others have the line threaded into the master cylinder.  You may have to use a new line with a banjo fitting.  No big deal because even with a new line it's still cheaper than buying a rebuild kit.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on September 10, 2019, 05:21:48 PM
Received the new spare master cylinder in black $9.53 US = $13.89 Au invoice slightly cheaper than I thought. I will resist selling this one off.
Link https://www.aliexpress.com/item/Motorcycle-Rear-Foot-Hydraulic-Brake-Pump-Refit-Rear-Brake-Master-Cylinder-Pump-For-Suzuki-Kawasaki-Honda/32922240225.html?spm=a2g0o.productlist.0.0.6e517eabhOs4jz&algo_pvid=a558c3ee-037b-4d5d-9fa9-b3f115d88b4d&algo_expid=a558c3ee-037b-4d5d-9fa9-b3f115d88b4d-1&btsid=109f83e2-fafd-4001-9785-cc3b843506c8&ws_ab_test=searchweb0_0,searchweb201602_9,searchweb201603_55
Regards Martin
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: tannerman917 on September 17, 2019, 11:28:43 PM
Just mounted up my new RMS... I didn't like how little travel I was getting with the piston threaded directly into the pedal, so I made a second joint for the piston that I'm gonna try.  I rounded off the threads on the end of the stem and drilled out a cap screw with a ball end mill so it rotates freely.  We'll see how it works once I get a new brake line for it.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: sammysnail on October 01, 2019, 10:10:01 AM

   I am always aware of, and grateful for, all those people who share their knowledge and experience via the internet. In this case I refer particularly to the Young Engineer, Martin, The Mighty Gryphon, and the others who have posted here.

   I try to help when I’m able to, so here are my experiences. It’s a bit of a rambling story but someone might find it useful. Settle back and get comfortable.

   My bike is a 1985 K100RS   with NO ABS, suffering from Magura seal failure.   

    I stumbled on the Chinese master cylinder concept when searching Ebay for a BMW rear master cylinder. “Chinese master cylinder, fits pit bike and BMW K100” (!!!). Further investigation led me here.

   The path I took involved using a 500mm braided teflon caravan brake line to replace the entire (non-ABS) brake line from the new Chinese master cylinder to the caliper. The line cost about $50 landed. 400mm would have been better, but the 500 was on offer.   Initially I was going to use a 90 degree banjo fitting on the master cylinder, with a female section silver soldered onto it. The banjo bolt was to be cracked to aid in bleeding.

   Then I changed my mind and decided to use a straight connection  that replaced the banjo bolt (nominally m10 x 1.25) with a straight adaptor (M10x1 female to M10x1.25 male), thus coming straight out the back of the master cylinder as per original. If necessary, to aid bleeding the footrest plate can be dismounted and inverted  (as detailed in someone’s post somewhere). The master cylinder arrived and it turned out that they used an odd thread for the banjo bolt. The diameter is  9.75mm, but the pitch is still 1.25mm, so a thread tap was used to open it out to M10x1.25. The banjo bolt came with a couple of Dowty-type washers, which was handy. A Dowty washer is a metal washer that incorporates a rubber o-ring bonded to the inside diameter. When the bolt is tightened the rubber deforms, but only to the thickness of the metal washer. This gives a great seal. It’s a simple and brilliant invention. Dowty was an hydraulics company, and among other things made air over oil suspension for motorcycles (Velocette and Panther come to mind).

   Because the caliper and the new braided line use different flares I made an adaptor to mount the new pipe to the caliper. This consisted of a short length of brake pipe (ex-Holden Commodore)  from the caliper ending in a female fitting (ex-Subaru),turned down and bored to take the pipe, to which was then silver soldered. This pipe was fitted to the caliper and then bent (in the fashion of the original pipe) so that it aimed at the centre of the hole in the  “C” section bracket on the side of the swingarm.  I  bought the M10x1  to M10x1.25 master cylinder adaptor across the counter at the local brake and spare parts place. It was about $5. I used one of the Dowty washers between it and the master cylinder.

   The easy solution is, of course, to use the original hose and pipe, screw the hose into  an M10x1.0 to M10x1.25 adaptor,  use a thread tap to open out the thread in the hole in the master cylinder and screw the whole thing straight into the back of the new master cylinder.... however..... a) I’d already bought the braided hose and b) this solution is not complex enough.
.
   If you’re in Australia you can use a Holden Commodore rubber front brake line to do the same job. You will need a joiner for the caliper end. This is a m10x1 double ended thingo that is hard to get. Or you could make or fabricate one (two sleeve nuts welded back to back might do it). The other end of this hose is a banjo type fitting.

   The pin-in-a-dimple operation of the master cylinder pushrod seemed rather crude, and like The Mighty Gryphon I considered a heim -type joint (rose joint on the threaded rod and a saddle on the adjuster bolt on the pedal. Move the master cylinder back one hole and brace it with a bracket).

    Then I tried a mock-up of the pin-and-dimple and decided that it was elegantly simple. I decided to put the dimple in the end of the master cylinder threaded rod so that I could retain the original rubber boot. I also put a nylock nut on the threaded rod until it just started to bind on the nylon. This helps to guide the pin into the dimple.

   The master cylinder that I got had mounting holes at 40mm centres, not the advertised 45mm. I had to file one of the holes to make it fit, which was a bonus as I was able to file it at a bit of an angle in order to bring the threaded rod more central to the tit on the end of the brake lever adjusting screw. This is not critical, as the rod can be moved through a fair arc. This rod has a mushroom head which fits into a recess in the end of the piston. A washer fits over the rod and is retained in the bore by a circlip. The rod is thus  spring loaded to the same axis as the bore, but will move from side to side with not too much effort. This assembly makes it easy to remove the rod to work on it (I used a lathe, but that’s probably overkill).

   The 500mm hose was a bit hard to route neatly due to its excessive length, so I made a bracket which hangs down from the front mounting screw which attaches the tragkorb frame to the footrest plate. This makes the hose hang in a loop in front of the final drive, keeps it away from the centre stand, and also reduces the strain placed on the hose where it joins the master cylinder as a result of suspension movement.

   I ran a new 8mm nitrile hose from the original reservoir to the new master cylinder. It was a reasonable fit on the barb of the 6mm reservoir pipe, and tightened up nicely with a hose clamp. Length 300mm, cost with clamps $7 from the local clutch and brake place.

   The system was bled using a vacuum bleeder, a first for me. I can see now why Martin uses a rigid jar with his to catch the fluid. I used a plastic soft drink bottle and just about pulled it inside out with the vacuum. Bleeding was quick and easy and there was no need to invert the footrest plate.

       Case closed.

Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on October 03, 2019, 11:26:55 PM
BE WARNED I'd be more concerned about the quality of the reservoir hose. I  was investigating a weep coming from just below the adaptor that went between the OEM reservoir hose and the Chinese hose. As I tried to wipe where the leak was occurring the hose just split and dumped the contents of the reservoir on the garage floor. I went to my favorite local brake guy to go and get a new hose and some brake fluid. He had a look at the split hose and said it was definitely not rated for brake fluid and said it was dangerous in this application. He shook his head when I said it had been supplied with the master cylinder.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on October 04, 2019, 12:57:19 AM
Just took a couple of pictures of the hose it split just under the hose clip. I was lucky it did it in the workshop and not on the three day ride I'm about to undertake. If it had split on the road it would have covered the rear tyre in brake fluid.
Regards Martin
 [ Invalid Attachment ]
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: sammysnail on October 05, 2019, 08:36:31 AM
Martin,
 The tubing that came with the master cylinder didn't fill me with confidence, but as I wanted to replace the entire tube, I wasn't using it anyway. I was about to use clear nylex tubing, but then I did a bit of internet research.

It turned out that very few materials are suitable for use with brake fluid. Those that seemed to be suitable were Tygon 2375 (clear), EPDM, Viton, and nitrile. None of them cheap.

The hose that the local place sold me is lined with nitrile rubber. Nitrile is apparently OK with brake fluid at low pressure and temperatures below about 80C. The tubing that I got is 5/16" and red on the outside , marked "EXE MULTIPURPOSE HOSE 5/16" X 50' (300 PSI)"

Time will tell

The following website has a bit of an explaination of the suitable materials:
https://www.pegasusautoracing.com/document.asp?DocID=TECH00147


By the way, something weird happened with my previous post. It was rather long, so I wrote it in a word processor document and then copied and pasted it into the reply window. When I pasted the text the word "p a n n i e r" was automatically replaced by the word "tragkorb", which is the German word for "p a n n i e r". Very strange. Did it again this time, which is why I had to use spaces between the letters.


.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on October 05, 2019, 08:55:36 AM
Thanks for the info on suitable hose materials.

I would caution against using EPDM hose on a bike.  The motor oil, fork oil, and fuel will turn that hose into black goo not unlike what happens to the fuel pump vibration damper.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on October 05, 2019, 08:59:04 AM
By the way, something weird happened with my previous post. It was rather long, so I wrote it in a word processor document and then copied and pasted it into the reply window. When I pasted the text the word "p a n n i e r" was automatically replaced by the word "tragkorb", which is the German word for "p a n n i e r". Very strange.
You're a stranger in a strange land, sammy. That's not strange here. Read enough posts and you'll be illuminated. Go with the flow. Tragkorb fairly rolls off the glottis. :-)

Thanks for your perspective concerning the Chicom brake cylinder installation.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: E30_Crazy on October 05, 2019, 09:05:28 AM


By the way, something weird happened with my previous post. It was rather long, so I wrote it in a word processor document and then copied and pasted it into the reply window. When I pasted the text the word "p a n n i e r" was automatically replaced by the word "tragkorb", which is the German word for "p a n n i e r". Very strange. Did it again this time, which is why I had to use spaces between the letters.


I believe it's a code built into the reply function of the website (not too sure on the technical terms). I have seen it change a couple different words. Alternator is, or was one. The Cafe/scrambler/street/etc builders often get hemmed up on "c l i p - o n s" turning into "strap-on".

That, or a Moderator/Admin frequently searches for terms and changes them manually.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on October 05, 2019, 09:16:07 AM
I believe it's a code built into the reply function of the website (not too sure on the technical terms).
Substitution Cipher. :-)
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: billday on October 05, 2019, 09:36:45 AM
I'm trying to make sense of this thought process:




Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on October 05, 2019, 10:00:35 AM
I'm trying to make sense of this thought process: . . .
It leaves more money for the memorial service and heirs. Every penny counts when intending to use a caisson flanked by fan dancers for conveying the cremains.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on October 05, 2019, 05:43:39 PM
Really, I enjoy living on the edge of disaster.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: sammysnail on October 05, 2019, 06:54:24 PM

Laitch, I am an egg.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: sammysnail on October 05, 2019, 06:58:47 PM

You're a stranger in a strange land, sammy. 
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: stokester on October 05, 2019, 07:29:07 PM
I'm trying to make sense of this thought process:

  • Question: How can I save a few bucks?
  • Answer: By buying the cheapest brake parts I can find.
Thought maybe I was the only one.  The original lasted 25 years or more and costs about $200.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on October 05, 2019, 07:40:51 PM
Laitch, I am an egg.
Your writing isn't reflecting that. Are you using a ghostwriter?
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on October 05, 2019, 07:49:23 PM
Thought maybe I was the only one.  The original lasted 25 years or more and costs about $200.

Actually, $269, and will probably be about $290 when the next price bump comes this winter.

Personally, I can't justify that kind of price for a couple die castings, two screw machine parts, and a couple rubber and plastic bits.  There is nothing magical in making a master cylinder.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Martin on October 07, 2019, 02:54:53 AM
Just got home from our 3 day ride to the Cane Toad Rally, one K1100, three K100 RS's, one K100 LT, one K75 RT and one K75 covered a fair bit of northern NSW. Total problems with the K's one RS mirror housing fell off and I blew a indicator dash globe that was fitted OEM in 1992. No problems with the new brake reservoir hose which is at least four times thicker and is rated for brake fluid and marked as such. In order to use the new hose which didn't fit the OEM reservoir I temporarily used the Chicom one until I get around working out how to fit the OEM one.
Regards Martin.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: sammysnail on October 07, 2019, 09:40:05 PM
While pondering the hydraulic ratio between master and slave cylinders I drifted into looking at racing type thumb brakes (rear brake operated by the left thumb).

By my reckoning the new Chinese-made K100 rear master cylinder at 14mm dia. requires about 15% more effort than the original 13mm one to get the same effect at the caliper. Brembo thumb brake master cylinders are also 14mm.

 Unless riders have massively muscular thumbs, I guess that the caliper cylinders on race bikes must be of considerably greater diameter than those on a Brick.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: The Mighty Gryphon on October 07, 2019, 10:32:59 PM
While pondering the hydraulic ratio between master and slave cylinders I drifted into looking at racing type thumb brakes (rear brake operated by the left thumb).

By my reckoning the new Chinese-made K100 rear master cylinder at 14mm dia. requires about 15% more effort than the original 13mm one to get the same effect at the caliper. Brembo thumb brake master cylinders are also 14mm.

 Unless riders have massively muscular thumbs, I guess that the caliper cylinders on race bikes must be of considerably greater diameter than those on a Brick.

I'm pretty sure that my master cylinder is 13mm replacing the 12mm original.  In about 20,000 or so miles of riding, the Chicom master cylinder has worked perfectly, being able to trigger the ABS on dry pavement, something the OEM master cylinder couldn't do.  Heck, the OEM was barely able to slow the bike down, even at parking lot speeds. 
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: Laitch on October 07, 2019, 10:57:44 PM
Unless riders have massively muscular thumbs, I guess that the caliper cylinders on race bikes must be of considerably greater diameter than those on a Brick.
Thanks for this observation. I was unfamiliar with this type of braking system. Certainly, hoses and caliper pistons must be sized correctly to effectively accommodate an increased master cylinder bore, but it occurred to me that for the thumb to work efficiently with a braking system, compound leverage would be effective in lessening thumb effort found in a 1:1 system like the Brick's cable/handlever assembly. I found this photo of a multiple-jointed thumb lever system. It seems to confirm that notion.

(http://www.motobrick.com/gallery/2/1601-071019225147.png)
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: szabgab on October 17, 2019, 04:08:20 AM

   My bike is a 1985 K100RS   with NO ABS, suffering from Magura seal failure.   

   The easy solution is, of course, to use the original hose and pipe, screw the hose into  an M10x1.0 to M10x1.25 adaptor,  use a thread tap to open out the thread in the hole in the master cylinder and screw the whole thing straight into the back of the new master cylinder

My rear master cylinder suddenly started to leak like a sieve. I have tried in vain to clean the inside of the bore (even though the rubber on the piston looks good enough), it still leaks. Anyway, I had this conversation bookmarked a while back (shame I did not buy a Chinese MC long time ago), so I have ordered one of these just now. My brake lines are still in good shape, but my bike is non-ABS, so I would need to replace the line to something custom made I guess, but Sammy's solution above gave me some hope of a cheaper solution. So my understanding is, the original line is m10x1.0 and the Chinese MC is M9.75x1.25? After re-tapping all it needs is this adapter to accommodate the old line? Thanks!
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: sammysnail on October 21, 2019, 02:03:38 AM
That's what I found Szabgab. I ran an m10x1.25 tap through the hole in the new master cylinder (it is best to first confirm that the thread on the banjo bolt that comes with the new master cylinder is indeed 1.25mm pitch - my new master cylinder does not look like the ones pictured above and there may be variations between the different ones available).

Then I obtained from the local brake service an adapter, m10x1.0 on the female end and m10x1.25 on the male end. The adapter screwed into the master cylinder, and the hose screwed into the adapter. The adapter moves the hose back about 25mm, but I don't think that this will cause a problem. I just had a look at my old hose and it should fit well in the new position.

The bore of your master cylinder  is probably 13mm and the bore of the Chinese one probably is 14mm, so you might find that just a little more effort may be required at the pedal. (ABS brakes have a 12mm bore so they would require even more effort) That is the theory, but in practice I haven't really noticed any difference.

Regards, Sammy.
Title: Re: Aftermarket Rear Master Cylinder Replacement Guide $10-$25
Post by: szabgab on November 03, 2019, 04:45:35 PM
That's what I found Szabgab. I ran an m10x1.25 tap through the hole in the new master cylinder (it is best to first confirm that the thread on the banjo bolt that comes with the new master cylinder is indeed 1.25mm pitch - my new master cylinder does not look like the ones pictured above and there may be variations between the different ones available).

Then I obtained from the local brake service an adapter, m10x1.0 on the female end and m10x1.25 on the male end. The adapter screwed into the master cylinder, and the hose screwed into the adapter. The adapter moves the hose back about 25mm, but I don't think that this will cause a problem. I just had a look at my old hose and it should fit well in the new position.

The bore of your master cylinder  is probably 13mm and the bore of the Chinese one probably is 14mm, so you might find that just a little more effort may be required at the pedal. (ABS brakes have a 12mm bore so they would require even more effort) That is the theory, but in practice I haven't really noticed any difference.

Regards, Sammy.

Hi Sammy, thank you for your reply. I was going in circles in my head with this.... Later I thought why not give a ring to a brake line specialist, and guess what, a new line with a 90 degrees banjo on one end and an m10x1 thread on the other would cost me something like 8-9 dollars. That is a no-brainer, I will get a new line and no adapters, etc... Obviously this ship from China is indeed very slow and my original rear brake master is puking brake oil whenever I step on the pedal...