You got Hi Folks,
Recently joined but this forum has been a wealth of great information so far. 
I’ve got a 1990 K100 RS that was in a bit of a sorry state so a good donor for a little customisation. 

So far I’ve sorted the brakes and removed the ABS, but not yet the electrics related. However once I had done these works I looked to charge up and start her for first time in a month. 

So the problem. The starter motor doesn’t initialise, or energise as it was. Previously when you turned the key prior to pressing the started your hear the pump for a second or two. Now nothing. 

I’ve directly powered the fuel pump from the battery and it runs, so I’m assuming all ok there. I read that the connector could cause issues so I measured the voltage from the green/white and the brown connector pins and got nothing. So I measured from the battery side of the two wires (snipped the cables) before the connector and still nothing. 

Pointers for next steps greatly appreciated. 
Oh I’m not massively knowledgeable on the pins layout/numbers etc so and handy tips well received. 

Thanks folks.

Side stand switch is ok???

robmack wrote:Side stand switch is ok???

BMW's cunning safety apparatus.  On an unmodified K100RS 4V moto, the pump won't work if the side stand is extended. While you're at it, check to determine if fuse#6 (the pump's fuse) is blown.  Verify that the fuse blade connectors aren't oxidized.

robmack wrote:Side stand switch is ok???

Side stand is up, however it’s a good place to start. In terms of testing the switch, any particular method? I’ll give it a good clean while I’m there.

First thing I would do to test the switch is to short out the connector it plugs in to. This is on the LHS of the bike above the battery.  Remove the connector and short out the plug.

Picture of the switch below.

Hi, On my K I have a switch on clutch lever. Won’t crank if it’s not pulled in. Yellow wires coming off the lever. Short them to be certain.
Good luck.

I’ll try these both at the weekend and feedback folk. Thanks for the input.

Ringfad wrote:First thing I would do to test the switch is to short out the connector it plugs in to. This is on the LHS of the bike above the battery.  Remove the connector and short out the plug.

Picture of the switch below.

Ringfad- what a call. I didn’t think this would be it. That’s what thinking gets you! Shorted the connection and the fuel pump whirred and most importantly the bike started! On now with sorting a new exhaust!

Exhaust......Remus? They are rather nice!!