Electrical Gremlins . . . .

HI All!
I had a bad battery which Bob's replaced under warranty. Everything worked fine except it wouldn't start with weak battery. I installed fully charged replacement and had bright oil, amp and neutral lights. Pushed starter button and starter made contact with ring gear and everything went dead. Sometimes I hear a noise when trying to start . . . like a switch. Tachometer will rise with no rpms. If I disconnect small wire off of starter I get bright lights but of course no start. When I replace small plug on starter no lights. I have tried new starter relay to no avail.
Could the main cable from battery to starter be bad?
Thanks,
Campbell Tellman II

1993 R100RT

Pull the Starter..

The starter itself may have shorted or has a bad winding.. or maybe the solonoid switch unit failed. Pull it out and take to an auto electric place..and have it checked. You can do some direct checking with a hot wire direct to the switch or the starter motor. Trace the wiring for good connections.

Careful of sparks.

I had my starter rebuilt.. The repair guy.. made it as good as new. There are modern replacements for less than the rebuild,, but it was not a Bosch of original make.

Jim

If everything else works as its supposed to, including the kill switch then I would suspect a bad connection at either the starter, battery or ground. After you've made sure these are all tight and making good contact, then if you still have problems then you could check for a voltage drop through the positive cable. Hook your volt ohm tester up and measure the voltage at the battery and at the other end of the cable. If there is any difference then you have a cable that has some internal issues and should be replaced. This is done at rest because as soon as you put any load on the cable ( try and start it ) the voltage will drop because of the load and you won't get a try indication of the condition of the cable.

This happened to me many years ago on a bike, not a BMW. I went to the expense of buying a new battery and then checked out the positive cable for a voltage drop. Sure enough there was a very small difference in voltage between the two ends of the cables. Replaced the positive cable and never had anymore issues.

The bad cable will drop the voltage just enough that the bike won't start. You'll hear the solenoid click but it won't engage the starter.

Worth a check and easy to do. Good Luck.