Author Topic: K75C Rehab  (Read 2429 times)

Offline johnclaude

  • Motobrick Curious
  • Posts: 28
K75C Rehab
« on: October 14, 2018, 06:35:20 PM »
Hi guys,

Just picked up my first BMW, a 1988 K75C, with 55xxx miles (fun discovery-the odometer turns over verrryyyy slowwwwlllyyy). Will follow the gauge rebuild guides and check out the gears/connections. It has been down on the right side, needs a new seat, new headlight or glass, new RH front turn signal assembly, and a thorough cleaning. Any suggestions on that front? Wire brush and simple green?
Found the original toolkit under the seat, and what looks like a homemade tool kit in the rear cowl. Does anyone know what that mystery BMW light is??Look forward to changing the fluids, plugs, and checking the spline conditions!







  • Aurora
  • 1988 K75C

Offline CNRED

  • ^ Proficient Motobricker
  • Posts: 145
Re: K75C Rehab
« Reply #1 on: October 14, 2018, 08:19:36 PM »
From Aurora myself, years ago.
Good luck with your build. I've got some S parts I'm not going to use, Fairings and the like.  If you need something let me know, shipping is not that great from Phx to Den.
  • Scottsdale, AZ
  • 1990 K75rt, 1992GSPD

Offline Martin

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Re: K75C Rehab
« Reply #2 on: October 14, 2018, 08:51:27 PM »
Does your bike have hazard lights? Does the mystery light flash? If you don't have hazards and it flashes it is a roadside hazard light. I believe some BMW cars had them, or could be a after purchase accessory.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline johnclaude

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Re: K75C Rehab
« Reply #3 on: October 14, 2018, 09:29:08 PM »
The mystery thickens....into a delicious stew. I can't get it to light up, mainly because I have no idea what kind of power port that is. We tried it in a cigarette lighter, but it was too small. I hit it with 12v, but nothing. I did figure out that the lighting mechanism turns and exposes what looks like a flashlight. Also, the yellow part has a little knob that allows you to turn the lens. Interesting....also, I'm not sure if my bike has hazards or not. I'm guessing not.

  • Aurora
  • 1988 K75C

Offline Laitch

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Re: K75C Rehab
« Reply #4 on: October 14, 2018, 09:51:20 PM »
The mystery thickens....into a delicious stew. I can't get it to light up, mainly because I have no idea what kind of power port that is. We tried it in a cigarette lighter, but it was too small.
If your moto has an accessory socket that will accept that plug, it will likely be under a small, round hinge lid mounted on the plastic coil cover where indicated by the arrow on the attached image.
  • Along the Ridley in Vermont.
  • 1995 K75T 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline The Mighty Gryphon

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Re: K75C Rehab
« Reply #5 on: October 14, 2018, 09:54:22 PM »
I can't tell from the photos, but in the top of the coil cover there may be an outlet that matches the plug on the mystery light.  That outlet isn't switched and is for auxiliary stuff like that light and for trickle chargers.

The outlet, BTW, is a BMW cigarette lighter plug, they were first used in German military equipment during WWII.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too

Offline Martin

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Re: K75C Rehab
« Reply #6 on: October 14, 2018, 09:56:31 PM »
The plug is called a Merit plug. There should be a socket located on the black plastic coil cover on your bike, it has a lift up cover. Merit sockets and plugs can be bought from some automotive shops or electronic stores. They should also sell an adaptor cable that goes from a Merit plug to a cigarette lighter socket. This allows you to plug in common accessories. My battery charger has a Merit plug installed to make charging easier, just plug it in to the fitted socket.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline johnclaude

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  • Posts: 28
Re: K75C Rehab
« Reply #7 on: October 14, 2018, 10:18:27 PM »
You guys are a wealth of information! I'll do some exploring, and report back. Thanks, everybody!
  • Aurora
  • 1988 K75C

Offline caveman

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  • Posts: 100
Re: K75C Rehab
« Reply #8 on: October 15, 2018, 06:07:43 AM »
johnclaude,
For your first BMW you got IMO one of the their best, just a great bike to ride on two lane mountain roads!
The black and polished aluminum look really sharp when cleaned up but a wire brush may be to harsh, try a tooth brush first. The bike looks like it will clean up nice, Purple Power is also good for removing dirt and stains.
Good luck getting it sorted out and keep us posted.
  • Kennerdell, PA.
  • 87 K100RT, 88 K100LT

Offline natalena

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Re: K75C Rehab
« Reply #9 on: October 15, 2018, 06:44:51 AM »
Congrats on your Brick, it'll detail up nicely. I had one of those lights as part of the required "Breakdown" kit in a 1997 318i when living overseas. If I recall, mine had a very long lead wire, spending it's entire life bundled up next to the first-aid kit and road triangles. I've had good luck with Rustoleum High-Heat brush on paint for the cases and forks. It takes a few coats, but doesn't seem to get dinged by pebbles/bugs. Good luck with the refresh!
  • East of Joshua Tree
  • 1987 K75s #0919
On Holy Quest seeking Techron equivalent for splines.

Offline johnclaude

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  • Posts: 28
Re: K75C Rehab
« Reply #10 on: January 13, 2019, 11:01:03 PM »
Today, I held my breath and removed the rear wheel to inspect the final drive and driveshaft. I was pretty nervous, since I bought this bike for $500 from a guy who I'm pretty sure jumped the title and may have bought it from an impound lot. For some reason, a decent amount of gross what smelled like gear oil came out of either the final drive or driveshaft, which was a surprise. Any ideas? What do you think of the DS/FD?




  • Aurora
  • 1988 K75C

Offline DavidATL

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Re: K75C Rehab
« Reply #11 on: January 14, 2019, 08:08:20 AM »
Driveshaft looks ok to me. Post pics after removing the gunk for a better look.

Final drive is splines are great but the input shaft seal is probably toast.  You may have just discovered a rare, prototype auto-lubing spline set up. ;-)

  • Atlanta
  • K75RT '92 w/ 24k miles (former bikes: '82 FT500, 80's GL500 Silverwing, 550 Nighthawk and FINALLY an '88 K75S) https://georgiaroads.wordpress.com including my #GA4corners route

Offline szabgab

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Re: K75C Rehab
« Reply #12 on: January 14, 2019, 08:14:44 AM »
Today, I held my breath and removed the rear wheel to inspect the final drive and driveshaft. I was pretty nervous, since I bought this bike for $500 from a guy who I'm pretty sure jumped the title and may have bought it from an impound lot. For some reason, a decent amount of gross what smelled like gear oil came out of either the final drive or driveshaft, which was a surprise. Any ideas? What do you think of the DS/FD?






john, I am sure, the more knowledgeable will chime in, but the ds seems quite nice to me. Compare it to mine, that was still driving the bike (but God only knows, how long that would have been the case) http://www.motobrick.com/index.php/topic,11767.0.html

Sulfuric smell is gear oil leaking from either the input seal on the fd or the output shaft seal on the transmission. If you are lucky, like I was, it is both :) Easiest to tell if you remove the driveshaft, if it is oily on it's body too it is output shaft (too), if dry only input shaft. From the pics however it looks to my untrained eyes an input shaft failure
  • Budapest, Hungary
  • K75S 1985 model

Offline DavidATL

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Re: K75C Rehab
« Reply #13 on: January 14, 2019, 09:09:41 AM »
  • Atlanta
  • K75RT '92 w/ 24k miles (former bikes: '82 FT500, 80's GL500 Silverwing, 550 Nighthawk and FINALLY an '88 K75S) https://georgiaroads.wordpress.com including my #GA4corners route

Offline The Mighty Gryphon

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Re: K75C Rehab
« Reply #14 on: January 14, 2019, 10:07:14 AM »
When photographing splines, clean them off and get the light to reflect off the top of the spline.  What you're looking for is a nice wide flat at the top of the spline.  That flat gets narrower as the spline wears.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too

Offline Chaos

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  • Mars needs women!
Re: K75C Rehab
« Reply #15 on: January 14, 2019, 10:18:39 AM »
That tool roll looks amazing for being 30 years old!  The CO2 & patch kit was included when the bike was new.  Those splines alone are probably worth what you paid, I'd say you got a deal.
  • sw ohio
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
2012 Ural 2WD sidecar (BMW's bastard step child)
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Offline johnclaude

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Re: K75C Rehab
« Reply #16 on: January 14, 2019, 10:44:33 AM »
Thanks for the replies, everyone! Sorry about the poor picture quality, that gear oil was nasty stuff. Should have cleaned it up better prior to photographing. Looks like I have some more disassembling to do to determine if it's the input/output shaft seals, or both! Super relieved that the DS/FD are in decent nick.
  • Aurora
  • 1988 K75C

Offline DavidATL

  • ^ Proficient Motobricker
  • Posts: 161
Re: K75C Rehab
« Reply #17 on: January 14, 2019, 10:52:17 AM »
I hear the FD input seal is a major job.

Mine weeps a bit (less than yours it appears), so I just keep an eye on on the level via the speedo sensor hole. Mine set for a several years before I picked up and leaks like this have lessened with regular riding. yay me!

Long shot, but there are oil additives that advertise that they swell seals a bit. Ie for transmissions and leaky engines. Clearly mixings some of that to new FD oil may put the whole drive at risk.
  • Atlanta
  • K75RT '92 w/ 24k miles (former bikes: '82 FT500, 80's GL500 Silverwing, 550 Nighthawk and FINALLY an '88 K75S) https://georgiaroads.wordpress.com including my #GA4corners route

Offline Laitch

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Re: K75C Rehab
« Reply #18 on: January 14, 2019, 09:33:50 PM »
I hear the FD input seal is a major job.
You've heard about it; now you can read about it here.
  • Along the Ridley in Vermont.
  • 1995 K75T 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303
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Offline johnclaude

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Re: K75C Rehab
« Reply #19 on: January 14, 2019, 09:38:53 PM »
Thanks, Laitch! Now thatís service!
  • Aurora
  • 1988 K75C

Offline johnclaude

  • Motobrick Curious
  • Posts: 28
Re: K75C Rehab
« Reply #20 on: February 04, 2019, 12:59:59 PM »
After cleaning the fuel tank and fuel pump and replacing the fuel level sending unit, I am not getting power to the fuel pump. Cleaned and replaced the #6 fuse, cleaned the 4 pin connector, verified that the pump runs when hit with 12 volts, and verified power to the female (harness side) of the connector...leaving the connector itself. Ordered some 4 pin waterproof connectors. Ugh. Should have just replaced the connector before replacing the fuel sender!
  • Aurora
  • 1988 K75C

Offline Brad-Man

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  • Posts: 358
Re: K75C Rehab
« Reply #21 on: February 05, 2019, 08:31:46 AM »
Congrats on the '85, but it looks like a naked and not a 'C' - the C had a fairing and windscreen mounted to the handlebars I always thought
..
  • Marietta, GA
  • '85 K100
Toys don't make the Man - Man makes the Toys...
'74 RD350
'75 RD350 w/Modified 400 engine, Chambers & MZB iggy

Offline mw074

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Re: K75C Rehab
« Reply #22 on: February 05, 2019, 08:49:34 AM »
Every " Standard " or " T " that I have owned was titled as a " C. " I was told by a dealer that they all were in the USA.
  • Michigan

Offline johnclaude

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  • Posts: 28
Re: K75C Rehab
« Reply #23 on: February 05, 2019, 10:31:55 AM »
Every " Standard " or " T " that I have owned was titled as a " C. " I was told by a dealer that they all were in the USA.

Yeah the VIN/title comes up as C, but it definitely appears to be a "Standard" model.
  • Aurora
  • 1988 K75C

Offline Laitch

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Re: K75C Rehab
« Reply #24 on: February 05, 2019, 10:38:21 AM »
Yeah the VIN/title comes up as C, but it definitely appears to be a "Standard" model.
The model C has a drum rear brake; the others don't.
  • Along the Ridley in Vermont.
  • 1995 K75T 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

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