Intermittant mis-fire

[knackeredMk1]

Three things before you panic -

Take the cables off the PV and feel the movement with your fingers. If it is sticking or not take the PV out and give it a good clean.

Take the cables off at both ends and check that they move freely and smoothly.

Take the cover off the PV servo and check if everything is OK - no missing teeth or clogging grit etc.....

[Active Rascal]

Steve,

I've just tried all this before even reading your reply.

The engine was re-built when the bike was, power valve was completely cleaned before, and it's still free as a whistle now!! The cables were brand new, and are not sticking. No mechanical faults inside the PV SM either.

Therefore mechanical faults eliminated; it must be electrical. I found no shorts or breaks on any of the 5 wires from the ECU to the PV SM. I Haven't checked wires to the throttle position sensor as it's difficult to get to. I'm not sure you can even test the TPS.

Therefore it's either the PV SM at fault (nothing looks obvious, but I have a spare to try out) or the dreaded ECU!!

[fallenmikethebike]

Have you replaced the HT lead from the coil? It's a relatively easy job, I always commender putting a longer lead in as it aids plug changing.
Mike

[Active Rascal]

What confuses me is that the PV was stuck in the most shut position, past the alignment mark where it sits at idle. I didn't know it ever actually closed this much.

If it turns out to be ECU, I have a spare, and we have our Greek friend (hopefully) to fix the Mugen one but I'll have to buy a new rectifier/regulator.

[pudzie83]

i had a issue like yours when i first got my mk2 and it ended up been the loom not sure where as i just replaced it with one that had very little use and mine had been tampered with and butchered, If your bike has has a regulator fail at any time (which mine had) it can fry wires causing a weak current

[Active Rascal]

Well, trip to Leisure Trail... new rectifier/regulator. Tried this on the bike with my spare ECU, no joy, still forcing the powervalve shut!! I tried a known working spare servo, still no joy!! Last one was to try a spare capacitor..... still the same!!

This narrowed it down to either the loom, or the throttle position sensor in the carb.

I re checked continiity, and found a faulty wire. This was showing as OK the other day. In the end it was the wire which does into on eof the pins had broken inside the ECU plug. It was a git to repair to be honest but I managed.

Not sure if I mentioned, but when fiddling behing the headlight I lost my spark completely. Upon closer inspection I found one if the wires had broken off my ignition switch!! The joys of offroad hey?! So for now I have bypassed it, unil I get it repaired or get a new one.

Probably a combination of all three things at the end of this, incorrect heat range plug for conditions causing plug fouling when at low revs, more recently powervalve problem, and no doubt the wire on the ignition switch didn't just break at once, so could have been another cause for intermittent poor running.

Anyway yesterday and today I've been working on the bike, re-built everything back as it should be, cleaned carb and put a fresh plug in.

I've uploaded a quick video to show you guys:

http://www.youtube.com/watch?v=lZ1x9Vy5 ... e=youtu.be

Cheers all.

Shaun.

[pudzie83]

you might want to be careful about bypassing the ignition and leaving it on as it eventually burns the stator unit/coils out on bikes i have a hidden push switch hooked up very simple and i never have to search for keys

[Active Rascal]

Does it?? Never heard this before?? Even when the engine's off?? I plan to fix my old one or get a new one ASAP anyway.

Cheers.

[fallenmikethebike]

you might want to be careful about bypassing the ignition and leaving it on as it eventually burns the stator unit/coils out on bikes i have a hidden push switch hooked up very simple and i never have to search for keys

No battery, or have I missed something.
Mike

[fallenmikethebike]

No key, more chance of the casual scrote making of with your CRM, less chance the insurance company would feel the need to compensate your loss.
Mike

[pudzie83]

you could be right about the battery bit, but ive had it happen on field bikes in the past i personally wouldn't leave it on

[pudzie83]

and as for the no key bit..... disc locks,ram posts,baby monitor,big chains,alarms and a baseball bat