87 K75 120k miles no starter action when start button pushed

[48882]

I had no trouble starting my bike for the short 4 mile ride to the doctor's office. I was in the office for about 45 minutes, and when i tried to start the bike to go home, there was no effort from the starter: no click, not sigh, nada. I did hear something soft which I think was the fuel pump. After several turn key on/off sequences, I had one more idea: I put the bike in 1st gear, pushed it so I could feel that the transmission was engaged with the wheel and then tried starting again. Voila! Started right up. Turning the key off/on again and it continues to start on demand.

May I have your thoughts on what caused this and what I might do to prevent it in the future?

 

[98lee]

There are several possibilities that could cause your symptoms.

It is very possible that your starter commutator is dirty or the brushes are very worn.

https://forums.bmwmoa.org/threads/starter-motor-overhaul-on-a-1992-bmw-k75s.53377/

Part # BMW-STRK007TK - Starter Repair Kit for Denso Starter - BMW K1, K75, K100, K1100, K1200 / To Repair BMW Part # 12 41 1 459 007 / EnDuraLast

Starter repair kit for BMW K Starter; BMW part # 12 41 1 459 007 Denso # 028000-8990 Part # BMW-STRK007TK

www.euromotoelectrics.com

It is possible the contacts inside your ignition switch are dirty.

https://forums.bmwmoa.org/threads/ignition-switch-cleaning.85331/

It is possible the contacts inside your kill switch are dirty.

https://forums.bmwmoa.org/threads/cleaning-replacing-start-kill-switch.92550/

It is possible, but less likely than the above, that your starter relay is going bad.

Bosch - BMW K Starter Relay ; 61 31 1 459 008 / Genuine Bosch Relay

BOSCH / Tyco Starter Relay; Tyco Original Equipment replacement for K models 1983 thru 1995 ; 61 31 1 459 008 / Genuine Bosch

www.euromotoelectrics.com

Check connection at starter and starter relay first.

 

[PGlaves]

Lee has it covered. If in fact you did hear the fuel pump start and run that would indicate that the switch worked at least. I think it is a dirty starter commutator. I had to pull one and clean it in a motel parking lot one fine spring day, long ago.

 

[AntonLargiader]

If you heard something, I suspect it may have been the starter motor spinning but it wasn't engaging the engine due to a slipping sprag clutch. If the engine wasn't turning at all, the fuel pump would not have run. Bumping the engine over and then having success starting it is exactly in line with past experience with the sprag clutch problem.

I posted maybe a year ago about it, and it is IMO highly likely for your case at 120k miles. The problem will gradually become more frequent and if you ride the bike a lot you may approach becoming stranded by it (I have personal experience with this!).

FWIW I have one such repair coming up at the end of this week. I'm waiting for the new sprag to arrive. To replace it, you need to remove the transmission, clutch, and bell housing. I figure minimum four hours, but every old bike is different and these are all old bikes. If you've never done it before and don't have experience with such deep repairs, figure two weekends.

Some people attempt to mitigate the issue by spraying some sort of solvent at the clutch through the crank cover opening, but that's not going to replace the metal that has worn away.

Here's the thread I started on it: https://forums.bmwmoa.org/threads/slipping-starter-clutch.104708/