This topic has been moved to Project Custom Motobricks.

https://www.motobrick.com/index.php?topic=15592.0

Hi folks, long time user, first time poster etc etc.
please let me know kindly if I miss step.

I’m a professional custom builder but this is only my second K Bike.

I have run the relevent searches but can’t find an answer. My questions are quite specific as I’ve been troubleshooting for a week now and I need to get this bike out to my client.

I’m currently rebuilding a 1992 K100RS 4v (abs no cat version.)
I have deleted the entire frame loom and replaced it with a motogadget M-Unit Blue system. This all works great (it’s not my first) However, I have kept the engine loom stock.

I have deleted the ABS as I’ve done a K1200/S100RR wheel and front end conversion.
I have deleted the side stand switch
I have deleted the clutch switch
I have a included the fuel pump relay & the fan relay

The bike was ridden into the workshop before disassembly and ran well. However, I have extensively troublshooted the obvious parts/systems when dealing with a no spark issue. The wiring, voltages, resistances all check out on the coils.

The problem:  After the rebuild I find myself with no spark on both coils. The fuel pump primes for 2 seconds at ignition on but does not come on during startup.

So my question is regarding the Motronic:
I have power going to pin 33 and 15. As I said, it sends the signal to prime the pump so it’s doing that bit right but it seems to be blocking proper startup procedures.

Does the Motronic, for security/safety reasons, block the startup procedure by restricting ignition and fuel?

I read that the H2o Sensor can send bad/no signal and that can cause this issue. Is that true? The one in the bike is not showing any resistance so I’ve ordered a new one but I could do with confirmation that that could be the problem.

If not, is there any other reason that the Motronic might block startup like this?

As I’ve said, I’ve run through the bike from battery to plug ends, I have continuity on all earths and the coils check out for resistance and voltages. (Besides, it’s both coils which suggests that it’s not the coils or the hall sensor. They wouldn’t usually go down on both sides at the same time.)

Any thoughts would be much appreciated.
I’ve about used up my own knowledge on this and a few other peoples to boot. I don’t want to start shotgunning parts at it (I prefer to hunt with a rifle) but I have swapped out the ignition amp (as I saw this was the issue in another thread) to no avail and the co pot (just because I had a spare in stock)

Thank you.

Jonathan

Bonus. It's good to see an occasional thread that has a quick fix.

Thank you much gents - I’ll try the cleaning. What do you think about the parts - provided I DO get in there. Bushings?

I would suspect that part of the reasoning for replacement is that the manufacturer has no control over how the machine is operated.  Are shifts being done without benefit of clutch disengagement, or is the operator riding like an old fart? 

I can see the shock loads when bang shifting being pretty tough on clutch bolts(as well as splines and transmission bits), as opposed to smoothly disengaging and re-engaging the clutch when shifting.  Shifting gently makes it possible for me to save a bunch of cash when I service my clutch.