Hi,

I have a problem with my 1986 K100RS 8-valve. I connected the battery momentarily incorrectly when fitting a new one, and the bike does not go at all now. There are no panel lights with ignition switched on and the only thing that works is the damn clock! I have checked all the fuses but none of the ones in the left-hand panel under the seat are rated high enough for an ignition circuit protection role, and on speaking with a so-called BMW Technician he said to check the relays or wires under the tank as they might be burned out or melted. There are of course none under the tank but under the seat. There are no apparent burnt wires - which relay is the relevant one to check? Grateful for any help as the bike is disabled now.....

Redrusty

First question: did you turned your ignition on with the polarity reversed on the battery?

No, but the battery did spark on first contact and once the battery was connected correctly the panel lights failed to light up and the starter did not work either.

I know that the electrical circuit is earthed through the starter motor and wondered if the motor brushes had corroded and stopped the earth path, but have rocked the bike in gear a few times but the bike is still dead....

I am not sure of the "relays under the seat" comment as the main electrical box, on mine at least, resides under the rear of the tank so that would be worth double checking and also the fuses with a multi meter just to be sure.

I think you were heading for a main fuse or fusible link scenario but as far as I am aware there is none.

I am pretty sure the starter only acts as an earth for the load shed relay which is lights, horn and indicators, so if it was faulty you would have no lights but maybe ignition?

The clock is actually a sign at least you have power to the instrument console so the main wires from the battery must be ok.

I don't know if it would have done the alternator any favours but whether that would cause the symptom you have is another question.

Regards,

Phil

Hi I will take a look see what is in the circuit diagram could you give us the chassis number please?
Regards,
K-BIKE

Chassis number is 0141622

Does anyone have any more advice as I have tested the relays and they are all checking out?

One thing I did notice was that the panel clock display disappears when I put the key in and turn it to the "on" position. I have not noticed this before. Is this normal or significant?

This may sound confusing but I don't think it is normal but may be significant in that it indicates the ignition switch is getting power and perhaps it is just a battery issue in that it is drawing current away from the clock.

Might be worth at least measuring the battery voltage with ignition of and on and if it checks out then we need to start looking via multimeter as to what is getting power and what is not.

Can you double check Fuse 1 is ok please.

Regards,

Phil