New old 1991 K100RS 4V

[riots100]

Shimmed up the rear ABS sensor, reset the ABS computer twice, ABS light extinguished.  Bike now has full functioning ABS I brakes.  (I didn't dare test the front though...)

[mophead]

Nice find.  The K1100RS bodywork will be hotter than the stock you have now.  Had one of these and it served me well.  Just service it and ride it.

[riots100]

I added a mirror leash for the left side mirror.  The right side bracket had a missing mirror post, so I ordered a new one and am awaiting delivery.


(I hope to never see this while I am riding)

I flushed the rear brakes, added new stainless steel rear brakes lines and then bled the rear brakes.  The fluid in the rear reservoir was light colored and clean.  I flushed it anyway and you can see the debris that came out.





I pulled the tank back to get at the front brake line that goes from the front master cylinder to the hard line junction going back to the modulator in anticipation of installing the front stainless steel brake lines.  I noticed a few things about what's under this tank that I didn't have on my K75.

There are two overflow lines coming from the bottom of the tank.  One line just slips on a tube spigot coming from the bottom of the tank and goes drains to the rear master cylinder area. I assume that this is the line that drains fuel and water from the tank cap area.  The other line is held onto the tube spigot on the tank with a hose clamp.  That line then runs down to a one-way valve, then down to the same area near the rear master cylinder.  What is the purpose of this second drain line from the tank?



On pulling the tank back, I saw that there is large rubber grommet that goes between the tank and frame, and that the bottom of the tank had some thick, heat reflecting material glued on.  It looks like it came from the factory. (a factory Johnny blanket perhaps?)  There is also an empty plug that is circled, what purpose does this serve?



And now for the main issue.  The aforementioned brake line from the front master cylinder terminates at a junction into a hard line going to the modulator.  That junction is buried very deep in the wiring loom below the tank, and sits under the tank mounting brackets/grommets on the frame. It is very hard to get to with a wrench and can anticipate many difficulties in removing the old line and installing the new one.



Is there a better/easier method to get to this brake line junction?

As I am getting deeper into this bike, I am more amazed at how clean everything is and the "like new" condition of all the parts.  I am beginning to doubt that I am needing to even replace the brake lines. (despite the gunk that came out from the flushing of the rear lines)

[riots100]

I finished up all the brake work.  I got the stainless steel lines on the front.  I put about 4-5 reservoir's worth of brake fluid through each system.  Hopefully that should be enough to have flushed the system. 





To get at the brake line junction under the tank, I had to remove the white retaining clamp that held down the two rigid lines to go to/from the modulator.  Then the line had enough play in it that I could get a wrench around each end.



Changed the oil with synthetic 20W-50. I'm going wait for the Eastern Beaver Headlight relay to come from Japan before I put the tank back in place.

[The Mighty Gryphon]

While the tank is off and you're waiting for the headlight relays you can wile away some time by adding a manual fan switch and maybe some LED driving lights to help the cagers see you.

[riots100]

Got the bike back together.  I plan on installing aux driving lights, but I haven't decided where I want to mount them yet.  The common places seem to be on the lower forks, near the brake calipers or under the front fairing.  I will want to make any mounting look like it came from the factory.  The headlight relays are in and working.  The headlight seems a tad brighter.

The brakes feel the same but at least there is fresh fluid and new lines.  All the other rubber hoses look new and the bike runs like a champ.  Although, while riding around last night, I noticed that the instrument light for the fuel gauge is not working.  I assume that there is one, since I see the fuel temp gauge all lit up.

I'm going to do another shakedown ride along Mulholland Highway on Saturday.  I'm thinking that she is good to go and that I'll tackle other issues as they come up.

[riots100]

Weekend shakedown ride complete.  The bike is in perfect working order. 

We went through a tank of gas in the Santa Monica Mountains and along the beach.

[riots100]

After some normal freeway riding, I'm getting some fuel weep-age from the top of the fuel tank around the filler cap.  The days have been warm but not excessively hot.

telltale fuel trails emanating from the fuel cap.


The fuel would run down tank to the knee pads


Nothing like this has occurred with my K75.  I took off the filler cap and examined the area around the filler hole and the inside of the tank.  All the plumbing is correct and in good shape.  I did notice some powdery deposit deterioration between the fuel cap and the tank itself.  I wonder what could be causing this mild fuel leak?

My best guess at the moment is that the fuel vapor is making it past the gaskets in the filler cap and condensing back to a liquid state and running down the outside of the fuel tank and down the side of the bike.  Any other thoughts?

When I popped of the cap and looked inside, I did notice some corrosion of the metal on the inside of the tank.





corrosion around the sending unit


Are these areas of corrosion something that I should address?  And if so, what would be the best practice to remove this corrosion?

[Laitch]

. . . My best guess at the moment is that the fuel vapor is making it past the gaskets in the filler cap and condensing back to a liquid state and running down the outside of the fuel tank and down the side of the bike.  Any other thoughts? . . .
When I popped of the cap and looked inside, I did notice some corrosion of the metal on the inside of the tank.
Are these areas of corrosion something that I should address?  And if so, what would be the best practice to remove this corrosion?

Purchase a fuel cap gasket kit (16119062461] from BMW and replace the cap's internal gaskets. The gasket (16111453690) around the fuel tank cap opening is a separate component. Replace that after you've cleaned off the rim where it is mounted.

You could remove and clean the sender per robmack's technique.

[riots100]

Finally received the fuel filler gasket set. The original parts had deteriorated with age and proximity to noxious fumes. This Video from Chris Harris helped quite a bit in getting the spring preload and positioning correct for assembly.






We'll see how well it works in fixing the fuel seepage problem with a full tank of fuel on a moderately warm day.  We should have plenty of those left here in SoCal!

[natalena]

Needed to mow the lawn ... so skipped that, and made a heat shield from a Domino's Pizza box and 3M 3350 aluminum tape. Rode around a bit, and by "the seat of the pants" measurements, it looks like the tadpoles are still swimming. Best part is, the board is covered on both sides with tape, so there's plenty to make a hat in case Chaos Inc. is trying to read my mind.

opps, sorry, meant for this to be under "what I did with my brick..." Damn interweb computee stuff.

*just reported myself to the moderators. Awaiting FBI investigation.

[riots100]

No worries, I don't mind the thread hijack!

I'm guessing that this was to mitigate heat transmission through the seat?

[natalena]

No worries, I don't mind the thread hijack!

I'm guessing that this was to mitigate heat transmission through the seat?

Thanks for the forgiveness. Yep, it was very toasty this past summer with the engine heat funneling straight to the seat pan. Concept tested some R30 insulation which worked great (like the Johnny blanket), but was cumbersome to deal with. I'd guess the cardboard heat shield drops the "real feel" on the seat by at least 20f, enough where the heat isn't noticed at all.

[riots100]

I finally finished doing some update work to my K100RS.  A while ago I purchased an RS fairing kit from TMG.  Not only did he send the fairings, but all the other parts and bits that would be needed, so much appreciated!

It has taken a while because the fairings would need to be painted to match the color of the bike.  I decided to take on the painting task by myself.  I wanted the paint work to be good and cheap. (so it wasn't obviously going to be fast)  A buddy from work who had some auto body painting experience, would be my mentor and helped out when things got more complex. (like the clear coat) 

I wanted the paint and body work to look good from 12 inches, and the color to be an exact match.  This meant that we would have to lay down a gray prime coat since the final color is affected by the prime layers. (we learned this the hard way)

The fairing panels were in good shape and only required some fill in where there some deep pebble and rock hits. (mostly in the belly pan) I learned that the way to get good paint is in the prep.  The painting is easy, the prep is hard.  I wet sanded again and again.  A few times I messed up on a paint layer and had to wait for it to dry and then sand it all down again.  My hands were wrinkled and sore from all the wet sanding.

This process dragged on for months and months, but we finally finished and I installed the newly painted fairings.

The Primer layer


Factory match paint from the local Auto Body Paint Supply




The Install


I also figured out a way to discreetly install a pair if high intensity LED driving lights just under the front cowling:



The finished look

(photo by Victory Jon)

I really like the look of these fairings, the bike has a clean, aggressive look that I prefer.  I am proud to say that this paint job will stand the 12 inch inspection and is a dead nuts color match.

It was a long, laborious process.  We got side tracked quite a bit with Covid19 lockdown.  It hit us hard and we had to think fast to keep the shop open and people working. We also lost a couple of elder statesmen of our business to the virus.

I would like to thank TMG for providing me the fairings and all the other bits and pieces and my work buddy/mentor for his time in teaching me.  I'm pretty pleased with the result.

[volador]

Outstanding work. Moto looks stunning!

Whose SS brake line kit did you install?

[Barry in IN]

That is beautiful. 

[The Mighty Gryphon]

Very glad I could help you out.  You have done an absolutely stunning job on your bike.

Well done!

[riots100]

Whose SS brake line kit did you install?

I installed the stainless steel brake lines from Spiegler. (https://spieglerusa.com)

[riots100]

While I have some of your attention, I'm having trouble figuring out how to mount the new Battery Covers.  I've searched the forum and the manual and can find precious little on battery cover mounting.

The old style, triangular covers attached at the cowl, on the tank with a rubber grommet and a soft frame mount at the bottom.




The larger RS style battery cover seems to mount in three places as well, at the cowl, the soft frame mount in the middle, and on a peg protruding from the knee panel.





Am I correct in assuming that those are the only three mounting points?  That these larger battery covers do not have a mount point in the grommet on the tank?

Also, I seem to not understand how the cover mounts to the rear cowl.  In looking at the cover, it seems that it mounts in a similar fashion to the front mount on the knee pad, but I cannot find any such hardware on the various parts fisches.  How does the cover mount to the rear cowl?

[volador]

K1100 rear tail cowl has right & left mounting pins for battery cover rear channel/hole slides on to

[riots100]

This is what I was afraid of.  On my K100RS, the rear pins are moulded into the battery cover, not the cowl.  My cowl just has a hole for the pins to slide into.

Are the pins moulded into the cowl itself, or are they a separate part?

[Laitch]

On Max's K1100RS parts fiche diagram it looks like a stud is screwed onto the rear of the cover, a short length of vacuum hose covers it then it is friction fit into the tail. Maybe Filmcamera will post up some photos and an explanation.

[riots100]

On Max's K1100RS parts fiche diagram it looks like a stud is screwed onto the rear of the cover...

Yes, I saw that too, so ordered two, one for each side.



They are brass and look like it should work, but the place in the cowl where these brass studs would fasten to are not compatible.  The hole in the cowl is about 8mm in diameter and there isn't any surface on the backside of the hole where a backing nut would get any purchase to firmly hold the stud. (and the hole is larger in diameter than the backing nut that came with the stud)  These studs are the same as the ones that are mounting in the knee pads.

I called the Max parts counter to see if they could offer any additional insights.  They came up empty as well.

There is clearly something else missing from this assembly.

[Laitch]

(and the hole is larger in diameter than the backing nut that came with the stud)  These studs are the same as the ones that are mounting in the knee pads.
There is clearly something else missing from this assembly.

I think that's where the short lengths of vacuum hose that I listed previously come in. I guess they slide over the post to increase its diameter and grip the hole's perimeter to prevent rattling.There's a washer in that assembly, too.
Does your cover look like this one? The post lug on the aft end of yours looks like it's missing half of its surface.

[riots100]

I think that's where the short lengths of vacuum hose that I listed previously come in. I guess they slide over the post to increase its diameter and grip the hole's perimeter to prevent rattling.There's a washer in that assembly, too.
Does your cover look like this one? The post lug on the left end of your looks like it's missing half of its surface.

Agreed.  The vacuum hose slide over the smooth part of the stud and fits nicely in the mating "clip" of the battery cover.  It's the same mounting concept on the front end of the cover where it "clip" to a rubber stud that is mounted in the knee pad.

The issue is that I don't see how the brass stud mounts into the rear cowl.  I don't think that a washer is the answer because there is no room on the rear side for even the nut to screw onto the shaft.

My panels look like this:


Similar, but mine seems to be missing a squarish stand-off where there is a square chunk of insulation missing on mine.

I wonder if there was some type of press-fit peg that goes into the cowl.

Clearly I'm not connecting all the dots...