Don't know if you've followed my other thread, but a large part of my problem ended up being that the under-tank brake master cylinder on my R100 had leaked brake fluid all over the starter relay, located directly below. Brake fluid is corrosive, and coupled with the funky way BMW wired the relay, made for a rather iffy primary power connection between the battery and ignition switch.
I had to replace the relay and clean up the contacts in the relay socket. But all is well and the total cost was under $10.
https://www.airheads.org/kunena/wrenching/296-starter-relay-issues
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Recognize that I have very little experience with models other than my '79 R100, and do not have access to an '83 R80 wiring diagram...
► However, it's very hard to make the entire electrical system go intermittent. Trace all the RED wire connections between the battery and ignition switch. My R100 uses the mini-cube type starter relay which is plugged into a relay socket. On my bike, BMW routed power from the battery (actually initiating at the starter motor terminal) into the starter relay on pin 87. Then on another pin 87, they passed the power through the relay and back out going to the ignition switch. The diagram on the side of the relay looks like this...
Study the schematic printed on the side of the relay and see that both terminal 87 are internally connected. So it wasn't so much that the relay itself was "good or bad", it was the condition of the relay terminals through which all the system power had to pass. So ANY problem with one or both of those terminals would shut down the entire electrical system. I suspect you need to inspect the relay terminals and relay socket very carefully.
[It's clear that BMW did not wire starter relays like this after ~1985, but without a schematic of your model I simply can't be sure which wiring style you have. Better safe than to continue with all the hair pulling.]
► As with any intermittent electrical connection on a motorcycle, we cannot rule out contact corrosion. There is simply too much road salt, battery acid, brake fluid, and other corrosive liquids being sprayed on a motorcycle as you innocently drive down the road. Therefore, after checking the contact tension on each electrical connection, I highly suggest you treat each connector with a small amount of No-Ox corrosion inhibiting grease before you plug the connection back together. This goes for spade terminals, relay sockets, harness plugs, et al. You'll only need the very smallest amount, so a tiny tube will do the entire motorcycle.
No-Ox electrical terminal paste
Hope this helps. 🙂
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Thanks for asking, yes it was a bad hall sensor. I ended up replacing the ignition can with an Alpha 3v system. The bike underwent a lot of work in the last few months. To the point where I'm considering a cross country trip in 2017. Any eastern airheads want to join in? 4 weeks or so. Gee ain't retirement great.
To the point where I'm considering a cross country trip in 2017. Any eastern airheads want to join in? 4 weeks or so. Gee ain't retirement great.
This statement deserves a thread unto itself.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Advertisement
