Author Topic: '87 K75 Revival....maybe.  (Read 3041 times)

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
'87 K75 Revival....maybe.
« on: January 08, 2018, 11:52:13 AM »

A little over a week ago, I finally called on a craigslist ad I'd been watching for a month. It was an 87 K75s that had been running when parked 5 years ago. It was pretty rough, cracked fairings, oil leak, broken turn signals, old gas, dead battery..etc but he was only asking $600. Due to some back registration, we negotiated down to $500 and I loaded it up.

It's my first brick, but not my first BMW. 20 years ago I had an R/90 with a documented 400k miles. It ran perfectly for the three years I owned it. Then about 10 years ago, I started riding G/s's. I had 3 r1150s of varying quality and loved them. But I started doing more intense dirt riding, and eventually sold my last one for a dual sport. Then I lost my job, and after a while, had to sell my dual sport too. For the first time in 27 years I was without a motorcycle. It was a tough year.

I've been picking up more work, and made the case to my wife that a project, if inexpensive enough, would be a good thing. I'd been trolling craigslist for months and this K75 kept haunting me. The problem with really cheap projects, is that the base bike at the end of it, is usually not very interesting. I came up on mid-70s hondas and had no desire to return. Most japanese bikes in my price range (less than $1500), were ugly, old, slow, beat to crap, and not worth my time.

But I've been brick-curious since they came out. So this seemed like a good way to get in to brick ownership without much risk. The bike, even if it didn't run, had enough parts to recoup my investment if it was totally dead. But since the PO had put 20k miles on it in 8 years without much trouble (he had kept a log book) before getting married and having kids, I was hoping it would just need a simple refresh before giving many more years of service. Pushing it around, the engine seemed to have compression, and it shifted through the gears.

So at the very end of the year I came home with a grubby '87 K75s with 96k on the clock, a progressive rear shock, a set of city bags, a set of the bigger bags, a tail-trunk, a stock seat and a corbin seat. He had bought it in 2004 for $1000 and did a lot of touring on it. The odo died in 2012 at 96,412, just before he stopped riding when his first daughter was born.Here's what it looked like before I washed it.





  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
Re: '87 K75 Revival....maybe.
« Reply #1 on: January 08, 2018, 11:58:58 AM »

I've owned a lot of project bikes over the years, and a good thorough bath is the first thing I always do. It lets me get familiar, and take notes on all the things I need to clean, replace, and investigate.


Once I washed it, I started stripping it down and hand cleaning the nooks and crannies.


My initial assessment:
All fluids in need of changing.
Wheels/Tires: good tread, but old, in need of replacement. No play felt in the bearings, both rotate freely without noise.
Brakes: non-operable due to lack of fluid. Rear master cylinder reservoir cracked and leaking due to UV.
Electrical: Unknown due to completely dead battery.
Tank: Gas cap hard to open, fuel pump gasket and in-tank hoses and proper clamps look to be in great shape. Slightly bubbled paint at the bottom corners revealed themselves to be several pin holes. At least partially resprayed at some point.
Rubber components: Replace. Fuel hoses cracked, vacuum hose cracked, crankcase breather badly cracked. Vacuum caps badly cracked, coolant tank sight hose discolored to the point of uselessness.
Wiring: Seemingly unmolested, and not too corroded at most of the connectors.
Body work: Poor. Both front turn signal lenses broken (one due to a crash, the other due to a ladder falling on the bike during an earthquake) Cracks in fiberglas, cracked windshield, center support bracket cracked around mounting bosses and barely attached.


[size=78%]

[/size]
  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
Re: '87 K75 Revival....maybe.
« Reply #2 on: January 08, 2018, 12:01:02 PM »
Master Cylinder





Pump





Pinholes






  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
Re: '87 K75 Revival....maybe.
« Reply #3 on: January 08, 2018, 12:06:09 PM »

My first step was to replace all the fluids. I started with the brakes. The front master cylinder was removed, cleaned in my harbor freight ultrasonic cleaner, and then refitted with fresh fluid. I got it to bleed quickly, and it built pressure, with the front calipers moving easily and not sticking on, but the MC leaked badly from the piston. Multiple removals, and gentle application of scotchbrite pads and 600 sandpaper to the bore didn't improve things. Luckily, my local cycle-salvage yard had 2 k75s! One C, one S. Picked up the whole throttle/switchgear/mc for $80. Cleaned it up, fitted it and the front brakes work well.


I changed the oil and filter (not too dark, no filings) and cleaned the oil off the bottom of the engine. No surprises, thankfully. I changed the transmission and final drive oil. There was a puffy halo of metal on the transmission magnet plug, but nothing large, it was essentially metal powder as I smeared it across a paper towel to check.


I removed and cleaned the airbox, put in a new airfilter. Removed the fuel rail, and cleaned the rust off of it. I removed the throttle bodies and cleaned them. I cleaned the ground wire for the battery, and the gang ground on the frame under the tank. Removed all the front body work, and replaced it temporarily with a standard headlight, and put the gauges on a piece of aluminum plate for now.


I used some permatex epoxy to seal the pinholes, and replaced the fuel lines/vacuum lines/caps/etc..with some fresh gas the bike started, smoked for a while, but ran well as far as I can tell. I took it for a little cruise around my neighborhood and it shifted through the first three gears, ran smoothly, had decent power and stopped smoking. I was feeling pretty lucky so far. With it running, I started making a modified list of issues.



The low fuel light doesn't turn on (tested the bulb, it's ok). All the other lights seem to light appropriately, except I haven't checked the temperature light operation, the bulb works. The odometer doesn't work. I hope to get injectors cleaned and tested soon. The four-pin connector for the pump is a little flakey. I got a later model rear brake master cylinder from ebay. I'm waiting on a new fairing bracket from BMW. Turn signals will have to wait. The forks need to get new fluid, I'm waiting on an injection syringe from amazon today.


I put it back in the shop to pull the FD and take a look at the splines. The final drive spline/shaft is toast.  :musicboohoo:


  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline billday

  • ^ SuperNatural Motobricker
  • Posts: 877
Re: '87 K75 Revival....maybe.
« Reply #4 on: January 08, 2018, 08:03:49 PM »
Great posts, great pictures. Keep at it, and keep posting!
  • New York State, USA 10977
  • 1985 K100

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
'87 K75 Revival....maybe.
« Reply #5 on: January 08, 2018, 08:51:34 PM »
Thanks. I had plans, and parts to keep going with the refresh but the poor state of the splines has made me stop and consider my options.

I think, before I do anything else I need to pull the transmission and check the input splines. If those are toast as well, then I may be better off in parting out the bike than continuing to revive it.

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  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
Re: '87 K75 Revival....maybe.
« Reply #6 on: January 09, 2018, 03:34:25 PM »
So there was probably a tablespoon or two of rust colored gear oil in the driveshaft/spline area. Is that evidence of a bad seal? Also, resting the FD on the disc as I remember reading somewhere, has caused fresh gear oil to seep out and puddle on the disc. Is this coming from the vent? (Everything is currently filthy enough to make tracking down the seepage a problem. )


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  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline The Mighty Gryphon

  • ^ Quintessential Motobricker
  • Posts: 3421
Re: '87 K75 Revival....maybe.
« Reply #7 on: January 09, 2018, 04:18:33 PM »
My final drive leaked when set down on the disc.  It came from the vent.  You have to keep the final drive upright to not have it leak. 

Normally they don't leak into the swingarm.  I had to replace the input seal on my K75RT final drive.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'91 K100RS "Moby Brick Too

Offline jakgieger

  • itinerant farmer
  • ^ SuperNatural Motobricker
  • Posts: 530
Re: '87 K75 Revival....maybe.
« Reply #8 on: January 09, 2018, 06:40:07 PM »
Good luck..if you need to finance your project, you could sell the city cases :bmwsmile !
  • Kansas USA
  • 1989 K100rs se
"What we've got here is failure, to communicate.  Some men, you just cain't reach.  So you get what we had here last week.  Which is the way he wants it...Well, he gets it.  I don't like it any more than you men do."

Offline mlytle

  • ^ SuperNatural Motobricker
  • Posts: 797
Re: '87 K75 Revival....maybe.
« Reply #9 on: January 09, 2018, 08:23:36 PM »
keep at it!

saved a few K75S's...

  • alexandria, va
  • 92 K75s, 94 K75s, 09 K1300s
Marshall
Project Thread "K75s Midlife Refresh"
http://www.motobrick.com/index.php/topic,7810.0.html
"K75s Midlife Refresh V 2.0"
http://www.motobrick.com/index.php?topic=10043.new#new

Offline TaosBrick

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  • Posts: 461
  • RedHotMotoBricker
Re: '87 K75 Revival....maybe.
« Reply #10 on: January 10, 2018, 11:37:06 AM »
Don't despair your FD/Driveshaft situation. When faced with the same thing on my '92 nekkid[size=78%] K75, I chose the to replace the whole bizness with an assembly from a first edition K100 which I found on eBay for a total of something around $200. The advantage to this setup is the 16 tooth spline arrangement, which I have been told is pretty much bulletproof, as opposed to the stock 22(?) tooth arrangement. The disadvantage, or additional advantage depending on how you look at it, is that the K100 FD is noticeably taller in ratio than the original. [/size]
[/size][size=78%]  My bike is in need of an injector cleaning, and the new setup makes things a bit more  sluggish, hoping getting 'em cleaned will improve that situation. as it is, I have to wring the piss out it while going up through the gears to make anything like reasonable acceleration happen. But then, a Klassic K of any stripe is not a crotch rocket by any stretch of the imagination. [/size]
[/size][size=78%]  The thing I DO like about the taller FD is lower revs cruising the slab at 80, which is where my whip spends many hours traveling cross country. [/size]
[/size][size=78%]  So I'd say just troll eBay til you find what you need. These bikes are real distance pigs, actually known to go 1,000,000 miles. Yours is a baby.  Good luck![/size]
Flog It Every Day - I mean, the BIKE!
'92 K75, '73 R75/5 Cafť,'89 Yam XT350
Expect Nothing, Be Ready For Anything.
- Samurai Maxim

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
Re: '87 K75 Revival....maybe.
« Reply #11 on: January 10, 2018, 11:50:32 AM »
Iím pulling the tranny today to check the splines. If they are good, Iíll repair the fd/driveshaft and motor on. If they are bad, Iím considering doing a paralever mod to it. I mean, Iíd need to buy a ton of parts off eBay anyway. With all the body work damage, and now the spline issues, the dark side of modding it calls to me. This isnít a clean, unmolested example in the first place. But I often have wild flights of imagination for bike projects.


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  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
'87 K75 Revival....maybe.
« Reply #12 on: January 10, 2018, 02:45:14 PM »
Got the transmission pulled. The splines look ok to me. The flats across the tops are evident and not too beat up. Thereís even evidence of some lube.

Judging by the mess, the rear main seal is leaking.




It looks like the tranny output seal is leaking as well. I wonder if the gear oil coating the driveshaft is from that seal and not the final drive.



The clutch/Spring plate is rusted and thereís moisture inside the clutch/flywheel area. I wonder why?




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  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
Re: '87 K75 Revival....maybe.
« Reply #13 on: January 10, 2018, 03:37:03 PM »
Reading back through the PO's maintenance notes. I'll give him credit, he took meticulous notes during his tenure. He replaced the clutch and seal at 85k, 11 years ago. It has somewhere north of 96k now. It's possible he didn't clean out the housing and the oil residue I'm seeing is just the remnants from then. I'm thinking that if it was still leaking, the clutch basket would not be rusty, but covered with oil residue, am I wrong?
  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline John Lang

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  • Posts: 100
  • John Lang
Re: '87 K75 Revival....maybe.
« Reply #14 on: January 10, 2018, 04:21:26 PM »
Rust-colored muck in the FD/Driveshaft area is probably Staburags moly paste flung off the rear splines. Normal, and good news.
  • Ottawa, ON Canada
  • 1987 K75C

Offline The Mighty Gryphon

  • ^ Quintessential Motobricker
  • Posts: 3421
Re: '87 K75 Revival....maybe.
« Reply #15 on: January 10, 2018, 05:45:05 PM »
Leakage at output shaft is probably the clutch o-ring.  They harden over time.  The seal is less likely, especially since it only has 11,000 miles on it.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'91 K100RS "Moby Brick Too

Offline rbm

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Re: '87 K75 Revival....maybe.
« Reply #16 on: January 10, 2018, 06:05:40 PM »
The main seal could leak if it was replaced flush with the housing, instead of 0.5mm proud.  It would ride in the same spot as the old seal and wouldn't do its job.  This was an install instruction from BMW.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/
2011 Moto Guzzi V7 Racer

Offline gofargogo

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  • Posts: 49
Re: '87 K75 Revival....maybe.
« Reply #17 on: January 10, 2018, 08:54:47 PM »
I cleaned everything up, and will check it again when I replace my driveshaft/FD. It's not that much more work to get the gearbox out. I decided that if there's a problem I'll replace the seal and oring then.
  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
Re: '87 K75 Revival....maybe.
« Reply #18 on: January 13, 2018, 07:39:35 PM »
After traveling for work for a couple of days, I woke up and decided to tear apart the front end for servicing. I knew the head bearings were stiff, and the fork oil was an unknown.
The head bearings were totally gunked up with hardened grease, but the races were in tolerable shape. I decided to service them and she how good I could get them before spending the money on new bearings. 20 minutes of soaking in mineral spirits, some scrubbing with a brass brush before an hour in my ultrasonic cleaner and they came out sparkling and free. I didnít see any pitting or discoloration on the rollers, so I packed them with grease and reinstalled them. Side to side movement of the triple clamps was smooth and easy now, with no discernible notching or hang ups.
The forks got removed, drained (of nasty black fluid) and refilled with atf. Iíll ride that for a couple hundred miles and then drain and refill again.


I took the opportunity to to replace the cracking fork seal protectors with rancho gaiters. Cheap, and they fit really well. One of the seals may be leaking a little, but Iíll ride it and see if it improves.


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  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline Martin

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  • Posts: 3224
Re: '87 K75 Revival....maybe.
« Reply #19 on: January 14, 2018, 12:30:52 AM »
Seals can sometimes be made to seal with a Seal Mate. These can be bought or made using a soft drink bottle. Look it up and copy it by cutting out of the bottle, shape is not super critical. And external soak with a rag soaked in ATF wrapped around them for a few days also helps.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
Re: '87 K75 Revival....maybe.
« Reply #20 on: January 14, 2018, 12:34:58 AM »
I rode it about 20 miles today running around the area. I love the sounds and smoothness of the motor!


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  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline mlytle

  • ^ SuperNatural Motobricker
  • Posts: 797
Re: '87 K75 Revival....maybe.
« Reply #21 on: January 14, 2018, 08:45:11 AM »
Working fast!   Nice!
  • alexandria, va
  • 92 K75s, 94 K75s, 09 K1300s
Marshall
Project Thread "K75s Midlife Refresh"
http://www.motobrick.com/index.php/topic,7810.0.html
"K75s Midlife Refresh V 2.0"
http://www.motobrick.com/index.php?topic=10043.new#new

Offline The Mighty Gryphon

  • ^ Quintessential Motobricker
  • Posts: 3421
Re: '87 K75 Revival....maybe.
« Reply #22 on: January 14, 2018, 09:18:21 AM »
hooked another one...
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '92K100RS White, '94 K75S Dakar Yellow
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'94 K75S "Cheetos"
'91 K100RS "Moby Brick Too

Offline gofargogo

  • Motobrick Curious
  • Posts: 49
Re: '87 K75 Revival....maybe.
« Reply #23 on: January 14, 2018, 12:11:00 PM »
Advice for those looking at bricks: be patient and buy one that hasnít been sitting unless you get it for next to nothing. These bikes really donít like to sit.

Good, clean running examples are shockingly cheap for what you get. Thereís no reason to buy an orphan unless you really like combing through every part of a bike and fixing neglect.


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  • Santa Rosa, CA
  • 1987 K75s
1987 K75s, my first brick

Offline billday

  • ^ SuperNatural Motobricker
  • Posts: 877
Re: '87 K75 Revival....maybe.
« Reply #24 on: January 14, 2018, 04:17:40 PM »
Man, have you drunk the Kool-Aid or what?

Welcome to the club!
  • New York State, USA 10977
  • 1985 K100

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