HELP save it or let it DIE! (85' k100rs)

[RBEmerson]

Actually, I think you've diagnosed part of the problem already. Clean up the wiring! And, yeah, clean the starter.

In general, apply Occam's Razor when troubleshooting. Yes, it's very remotely possible that the magnets in the starter have failed because a coronal mass ejection from the Sun induced a geomagnetic storm of sufficient intensity to alter marginally magnetized magnets. But it's more likely the wiring is boogered or the brushes are shot.

IMHO, people who would part out their own bikes would also sell their own children. (Only partially joking...)

[98lee]

Another possibility is a dirty ignition switch causing a voltage drop to the coil side of the starter relay. The starter relay has a minimum voltage at which it will activate.

A sign of this problem is low voltage at the top fuse (like 6v) with the key and kill switch on and fuse in, but good voltage on the right side of the fuse socket with the fuse removed.

But your issue still sounds like dirty starter if you are getting any voltage to the starter. The above is a cause of sometimes you get voltage to the starter and other times you don't (intermittent solenoid actuation).

[DARKCLOUD]

Have you had the bike to T&B cycles in Linton? I have had several wiring problems solved there. Jon

[42906]

You're a lot like me, 2old2rock. Think very worst case instead of the simple. I'm with 98lee. Pull your starter and clean it. Then ride!

I am voting for a faulty starter as well. While it is apart, considering the mileage on it, I would put two new carbon brushes in it. They are a necessary part of the ground circuit on our bikes and not at all expensive.
When you disassemble it, take time to mark each end and the body so it goes back together correctly without a bunch of guess work. When it's apart, it is tough to remember which end went where unless you make some discreet marks on the exterior.
Clean the rotor and interior out with electrical parts cleaner, install new carbon brushes and let us know what happens.

[42906]

Another possibility is a dirty ignition switch causing a voltage drop to the coil side of the starter relay. The starter relay has a minimum voltage at which it will activate.

A sign of this problem is low voltage at the top fuse (like 6v) with the key and kill switch on and fuse in, but good voltage on the right side of the fuse socket with the fuse removed.

But your issue still sounds like dirty starter if you are getting any voltage to the starter. The above is a cause of sometimes you get voltage to the starter and other times you don't (intermittent solenoid actuation).

Failed ignition switches are not intermittant in my experience. Now I keep a known good spare in the storage compartment.
Btw, you can remove the switch part from the lock so you can change switches without re-keying or having a separate key for the ignition and your old key for the gas cap, seat lock and saddle bags.

[98lee]

Failed ignition switches are not intermittant in my experience. Now I keep a known good spare in the storage compartment.
Btw, you can remove the switch part from the lock so you can change switches without re-keying or having a separate key for the ignition and your old key for the gas cap, seat lock and saddle bags.

That is incorrect. I JUST got done fixing my bike. It had the classic dirty starter intermittent starting symptom. I cleaned and installed another starter. Same symptoms. So I started to troubleshoot. Found intermittent low voltage to the coil side of the starter solenoid. The solenoid has a threshold voltage (around 6v) under which it will not pull in. Some times when I would turn on the key, the voltage to the coil was 9v and other times 5.5v. When it was above 6v, it would start. When below, no start.

The voltage for the coil of the starter (and the IGNITION COILS, and the headlight and a bunch of other stuff) all go through fuse #1. With the the fuse pulled, I was getting battery voltage to the fuse. But when I put the load of the headlight and the coils, etc. on it by reinstalling the fuse the voltage dropped considerably indicating a bad connection upstream. That fuse is fed by the ignition switch.

I cleaned the switch contacts and now I have battery voltage every time to the starter coil. AND my horn is WAY louder.

This should be a periodic maintenance test. Check the voltage at the fuses with the fuses installed key and kill switch on. If any are low, suspect dirty ignition or kill switch. It's a simple test that can head off no start conditions and random dying.

[42906]

Huh, learn something new every day. Thanks.

[98lee]

Huh, learn something new every day. Thanks.

That's why we're all here, to try and learn about these great Flying Bricks!

I wasn't aware of this issue two days ago. Always had heard that starting issues were dirty starter. Now there are two possibilities and one of them (the ignition switch) can be diagnosed with NO disassembly other than removing the fuse block cover.

[montec]

Just went through my ignition switch to clean things up.

Picks of the switch are here:
http://www.bmwmoa.org/forum/showthre...d=1#post781633