New Bmw K75C owner from Houston TX

[Mavebrick]

Just got myself a 1986 BMW k75c. I have always been interested in the flying brick and finally bought one. I took it on a test ride and loved it but it had some gear shifting issues particularly to first gear. I am currently going through checks and have checked transmission and rear fluids and they are looking good. I need to change engine oil next. I tried taking plastic cover off to check front brakes but cannot tell if they are good i may have to unbolt the caliper to look at brake pad. I hear squeaks when braking which is making me wonder about brake pads. I adjusted and wd-40 some parts of the clutch cable to get the right dimensions and slack and it seems to shift better today after adjustment and lubrication. The one issue is i find myself getting false neutrals into fourth and fourth to third sometimes and the gear indicator goes blank at times. Still feeling out the bike but I am in love with the engine and its smoothness. I hear a huge clunk sometimes when getting off from first gear from a stop. Here’s my brick:

[Chaos]

Not going into first could be the clutch not disengaging all the way, adjustment should help but check the cable where it meets the clutch handle on the handlebars, there's a little barrel that fits into the handle and needs to rotate.  If it freezes up the cable starts to fray there and then breaks.  Lube that barrel occasionally.

[Laitch]

 

[Past-my-Prime]

I’ve developed the habit of “preloading” the shifter when upshifting, apply a bit of pressure with the top of your foot, then clutch and complete the shift into gear. It became second nature quickly, and I no longer have false neutrals between 3 & 4 or 4 &5 as I previously did.
Only downside is occasionally it’ll occasionally autoshift with that, even without squeezing the clutch, so I can’t preload too much!

[Mavebrick]

Thanks for the tips, really appreciate it. This is the smoothest motorcycle I have ever ridden!
The clutch adjustment and lubing cable seemed to have done the trick and it seems to shift fine. Odometer has stopped working at  51k miles so not sure the deal with that and if there are aftermarket replacements .Threw seafoam in the gas tank and crankcase and plan to run it a bit this weekend and then change engine oil.

[sooprvylyn]

Yeah that k75 engine is like riding a stick of butter. Welcome to the party.

As another poster mentioned, lube the clutch cable barrel with some grease(not oil). That will keep the cable from eventually snapping on you. While you are changing the oil, it's a good time to also change out the gear oil in the transmission and the final drive.

If you are feeling up to it, you might consider also lubing the rear drive spline and inspecting it. It's about an hour job your first time doing it, but it's pretty easy. Just throw it on the center stand, remove the rear wheel and unbolt the final drive. There are 2 splines on the drives shaft. Use some visegrips to grab the drive shaft and smack em with a mallet to pop it free so you can lube the transmission side. Use a high moly grease for this. It goes back together really easily too. You should relube those splines with every tire change while you have the wheel off to keep that drive shaft in good shape. It's a known failure point if it's ignored.

[Laitch]

The main cause of worn splines on shaft couplings is the sliding contact between them during operation. That wear is called fretting. Fretting doesn't occur on the spline couplings of the driveshaft's universal joint with the transmission output shaft because they are clipped together; that union can be lubed at 16K–40K miles intervals when the final drive, swing arm and transmission are removed to inspect and lube the transmission and clutch disc coupling splines; however, as soopr indicates, it's widely accepted as important that the driveshaft rear socket splines and the final drive pinion gear input shaft splines need the lube every riding season or tire change to control fretting wear.

If the maintenance history of your Brick is unsubstantiated, it would be prudent to remove the transmission at your earliest convenience to inspect then thoroughly clean and lubricate the clutch hub/transmission input shaft splines with a stiff paste containing 50% molybdenum, or a paste containing either graphite or barium.

[Mavebrick]

Thank you. I plan to replace tires in the near future and will lube the splines at that time. I have lubed the clutch barrel near the handle as well. Been taking little rides around and notice a substantial amount of heat generated at the tank area. Is there any trick to reducing the heat or anything y’all put to mitigate it?I peeked into coolant overflow little tank on right side and the coolant level is between max and min. Thank you and appreciate all the tips I get on the bike.

[sooprvylyn]

Thank you. I plan to replace tires in the near future and will lube the splines at that time. I have lubed the clutch barrel near the handle as well. Been taking little rides around and notice a substantial amount of heat generated at the tank area. Is there any trick to reducing the heat or anything y’all put to mitigate it?I peeked into coolant overflow little tank on right side and the coolant level is between max and min. Thank you and appreciate all the tips I get on the bike.

A bit of heat riding a brick? Welcome to bricks. They are known to run a bit hot for the rider and stock setup has the radiator fan pushing hot air kinda up and over the airbox right into the tank and the riders thighs.  It's pretty normal. My k75 had silver reflective matting on the underside of the tank to help mitigate heating up the tank. It also had a thick rubber tank pad thing that went down the sides a fair bit which blocked the hot air hitting my thighs. Even on my modded k1100 that is wide open under the tank blasts my thighs with hot air. It's part of the joy of k bike ownership.

Btw, the tanks are double walled, which probably insulates them a bit from this heat situation.

[Chaos]

+1 on some foil insulation under the tank.  Another heat problem is the fuel pump runs constantly, excess fuel is recirculated to the tank so you have literally have the engine heating the fuel tank,

[Past-my-Prime]

Some people have put fuel coolers in the return fuel line.

[sooprvylyn]

Some people have put fuel coolers in the return fuel line.

interesting....never heard of this before.  I need to look into this idea.

 

Another heat problem is the fuel pump runs constantly, excess fuel is recirculated to the tank so you have literally have the engine heating the fuel tank

I dont know how much the engine is heating fuel since the fuel really only goes through hose and fuel rail on a 2v K(i dont think there is a FPR on the 2v but I could be wrong...i am wrong). The rail is a bit insulated from the engine with rubber grommets too.  Might be a little bit of heat transfer, but I'd suspect the bulk of it is from the radiator fan, and maybe some from the pump.

[Laitch]

Here is a comprehensive thread about fuel coolers for Bricks. The fuel rail also picks up heat. Plenty of riders in hot climates use them, and use methods of insulation, too, BMW offered various means of mitigating engine heat's affecting the fuel. There is a document here that discusses various ways of mitigating heat. The link is below. Riders of naked Bricks don't feel heat as persistently as riders of RT and RS models.

[frankenduck]

Btw, the tanks are double walled, which probably insulates them a bit from this heat situation.

Urban legend. They're single-walled.




Odometer gears are most likely your issue and can be repaired:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/odogearreplace/odogearreplace.htm


The bike has a standard, not K75C, headlight.

Here's what a C looks like:



You can do a VIN lookup to see what it came from the factory as:
https://www.mdecoder.com/

[sooprvylyn]

I could swear I felt a substantial thickness to the tank when I had mine empty and prepping for paint....and i know for sure I've read that a few times too.

 Your photo sure does appear to be single walled tho, so good to know.  Would make repairing dents a lot easier than I thought they'd be.

[sooprvylyn]

Here is a comprehensive thread about fuel coolers for Bricks. The fuel rail also picks up heat. Plenty of riders in hot climates use them, and use methods of insulation, too, BMW offered various means of mitigating engine heat's affecting the fuel. There is a document here that discusses various ways of mitigating heat. The link is below. Riders of naked Bricks don't feel heat as persistently as riders of RT and RS models.

thanks for the link.  I may look at installing one for my hot texas rides.

[Martin]

 After playing with a home made cooler that only worked at 80 Kph I went old school hot Holden solution.   https://www.k100-forum.com/t14096p50-overheating-fuel-solution-mk1-new-improved-mk2#189438. I've been running a heat shield since 2018 and it's staying as the bike is a lot cooler. IMHO it was better to stop the fuel overheating in the first place than to try and cool it down once it had heated up.

Heat Shield Black 1.jpg (39.64 kB . 768x576 - viewed 463 times)
Black Heat Sheild 2.jpg (58.1 kB . 768x576 - viewed 494 times)

[Laitch]

K75C with C headlight cowl.

[Mavebrick]

Thanks for the tips guys. I am about to try a “solution” that probably wont work but I will report back nevertheless. I put a sheepskin seat and put heat resistant silver tape below the sheepskin. Taking it for a ride in the beautiful Texas cauldron..i mean heat and will see how it does.

As for the bike type I checked the vin and it is a K75C and previous owner told me someone replaced the stock headlight covering with the current cowling on it.he did recommend i buy the original and replace it as he liked the look of that better.

[Chaos]

just to confuse the issue, it could also be a K75T with the windscreen removed.  BMW USA took a C, changed the cowling, added higher bars, windshield, touring seat, bags and maybe running lights.  I think it ran 86 and 87