Annoying K75S electrical glitch

[Lord Snooty]

Any ideas on this one?

My K75S has developed an intermittent electrical glitch. Every now and then whilst riding along the engine will cut out and restart in an instant. The closest analogy I can give is that it is as if the ignition has been switched off and back on in a fraction of a second. I have checked the earthing strap and the battery connections, and the battery is pretty new.

So where do I need to start looking next?

 

[Edward]

I had a K100RS that did exactly that shortly after buying it new. It became gradually worse and was cured by a replacemnet ECU. It might be worth having a look at the large multi pin connecter for cleanliness. Please be aware I know sweet FA.

 

[electric_monk]

I would suggest the starter motor brushes, I don't remember all the technicalities but they are part of the earthing circuit relating to the load shedding relay. It is a cheap fix that can be done in less than an hour.

 

[Timolgra]

As well as the above ...........Bottom of the ignition switch, mine did that.
The contacts are probably a bit loose, fixed mine with a cable tie I think

 

[seahorse]

+1 for all of the above but I would start with checking the ECU plug, then the ignition switch. I have a spare starter and an ECU if it turns out to be either of those.

 

[Lord Snooty]

Thanks all.

I'll start with the easy checks first so will do the ECU plug and then the ignition switch, Tim standby the phone in case I need to have a chat.

I replaced the starter motor and alternator brushes about a year ago but if the above checks fail to resolve the issue I will whip the starter motor out.

Seahorse - many thanks, if it turns out to be the ECU I will take you up on your kind offer.

 

[Steptoe]

Ignition switch or the ignition switch wiring.

 

[seahorse]

Thanks all.


Seahorse - many thanks, if it turns out to be the ECU I will take you up on your kind offer.

I don't have my K75 any more but I still have tons of bits, PM me if you ever need anything. I also have a complete genuine BMW shim kit

 

[Lord Snooty]

i cleaned the ECU plug contacts last night and started it up, I gave the ignition switch barrel a real good vigorous waggle and pulled at the wires and the bike continued running ok. If the problem was in the ignition barrel and wiring I would have expected it to have cut out so I think the problem is elsewhere. I will take it for a test ride tomorrow and see if the problem recurs, if not then it may have been dirty ECU plug contacts, if it does then the next check is the starter motor brushes.

 

[Lord Snooty]

Update

i took the bike out for a test ride and the problem is still there so back to the garage and out came the starter motor. Opened it up and the brushes are absolutely fine, so put it back together, refitted everything and tried to start it - click, nothing, tried again, nothing and then noticed smoke coming up from the starter motor area. SHIT! Switched off ignition, battery terminals red hot and the power wire to the starter also red hot, bollox I have obviously caused a dead short inside the starter. I think the smoke was from the melting insulation shroud on the starter motor power wire.

I have stripped the starter motor again and it looks ok but:

1. Is my starter motor now bolloxed?
2. Might I have caused other damage elsewhere?

What a twat!

 

[Packer]

If you caught it soon enough there may not be much damage, even the cables that were smoking. If you were a tad slow to notice however......................................................................

 

[Lord Snooty]

If you caught it soon enough there may not be much damage, even the cables that were smoking. If you were a tad slow to notice however......................................................................

Give me the bad news Packer, I can handle it