Hi,
Bad moment this afternoon, after successfully wiring in the headlight relay mod, I went to take the K100RS out, turn key, dash 
Lights all on, press button and nothing. No click from starter relay or starter motor. All other systems seemed to be whirring or clicking as usual. Battery fully charged and delivered 12.5v. All connections appear ok.

I have checked power continuity across the relay with the button pressed, power in and nothing out. I also checked power in through the connector block and that was ok. Last start up was 4 weeks ago after a spline lube and unusually it failed to fire after lots of cranking. When it did fire we put it down to a loose connector to the ECU or fouled plugs from prior slow running on choke. 

So I think the starter relay has failed after the previous prolonged cranking. I cannot order another relay until Monday, so is there anything else I could check or do in the meantime?  I was thinking of tapping the relay tomorrow just in case it loosens the contacts but don't really think that is a long term solution...

Many thanks.
Regards
Nigel

Did you try starting with pulling in the clutch? Normally the starter relay fails when trying to start with low battery power and the relay welds itself and you can't stop it starting any more. That's not your problem, I appreciate that. Did you measure the power to the starter relay (the switch wire)? I wouldn't throw a new starter relay at it without further testing some, they're pricey!

Alternatively you're continuous cranking has burned the contacts of the relay, but I would verify that by opening it up.

No I did not try pulling the clutch. I will check that in the morning!  'Voltage to the switch wire', all wires feeding the relay were delivering 12.5v, this was my first check as I was concerned that my work locating the headlamp relays in the relay box had upset something but all appears ok. And yes, i now unfortunately know how much the relays are!
Many thanks.
Nigel

Consider fitting a contactor ('starter relay' or 'starter solenoid') from a Japanese bike instead - see post 31 here:

https://www.k100-forum.com/t10428-comberjohn-s-ghost#129762

Get one with the rubber mounting ring already on - most on ebay are like that but I've seen a few without. Note my comment about having a non-standard relay box. The contactor will quite happily go in the space under the original starter relay (you may have to make the mounting bracket but it's only two right-angle bends in a bit of strip steel) and you'll be able to bolt the OEM battery cables straight on. However, you will have to replace the connector that holds the black/yellow and brown/red wires for something to suit the terminals on the contactor.

Starting with the clutch pulled in made no difference, unfortunately.

I have found the OE relay for a reasonable £18.98 plus the postage, which is a bit pricey at £8 but it is coming from Germany.  
http://www.sparepartstore24.co.uk/1154775-bosch

Dai, thanks for the advice but I will stay original for the moment.

Regards
Nigel

OK, sounds a bit like Hutch's bike...

So you verified that there is 12V put onto the starter relay wires (brown/red & yellow/black, the two contact plug that fits into the relay) when you press the starter button I understand, but the relay doesn't switch. In that case the starter relay is duff I'd say.

Buy a new (or alternative one) and don't fit it, but connect it to the two 'control' wires and see it it switches when you press the button (you could probably 'jury rig' one of the little relays; use the 'horn' one) to see if it switches as intended.

I will put the order in tonight, should be with me mid week and will post up what happens. Hopefully the sound of a Brick on tickover!