I took the carb off something around 20 times today, spent two cans of Carb Cleaner on it and blew out every little orifice I could see (and I even used a magnifying glass). What's strange is that it's not firing even when pouring gasoline directly through the spark plug hole. Must mean it's decided to fire a spark at the completely wrong time. Even checked my reed valve. Oh yeah, I've tried bumping it, dragging it with a car and even hand starting it on the stand (put it into 6th and turn the wheel by hand very fast). Nothing worked, but still haven't given up on it. I'll make a flywheel puller on Friday to try and see if the stator has loosened/spun or did something else. If not, I'm in for a complete Kokusan conversion. Where does one find these?

You bike should fire with the timing anywhere between TDC and 20 degrees before TDC. Mark the flywheel / crankcase with indicators of those positions. Attach a strobe light and spin the engine with a power drill. Spark plug out and earthed with a little oil down the plug hole. You will then soon see when (if?) a spark is occurring. The spark should easily jump a 0.9mm plug gap out of the cylinder.

Edit - Check the little sprung loaded pin on the float valve plunger moves freely with not notchiness.

Edited February 22, 20179 yr by dadof2

Almost sounds like a grounding issue. Check all earths and connections over again. PS double check all the pins in the cdi are making contact.

Edited February 22, 20179 yr by lineaway

while I suspect it is an ignition/grounding issue one other quick one to check:

Is it getting enough air?

have you recently cleaned and oiled the air filter?  too much oil = not enough air flow or sucks in more oil than fuel and  can cause poor running condition.

 

easy check, fire it up for a few seconds with the air box disconnected.

I bought my Kokusan ignition as a complete kit from trialsbikebreakersuk ebay store. I was lucky to get it as a kit but usually you can find the parts separate or ask them to bundle it.

The spark I get while kicking it over (with the plug grounded on the cylinder) is a blue to white color, and quite strong for slow kicking. The fuel cut off needle valve (with the rubber tip) is moving freely both ways. Haven't tried putting the float level back to 18.5, will do tomorrow. Also, tried starting it without the airbox, no joy either. While kicking it over a lot I do get a bang and a pop out of the exhaust on occasion. Maybe it is a grounding problem, but how come I've got spark when I lean the plug on the cylinder but not when the plug is screwed in? baffled...

Feel like a bit of an idiot now... Couldn't wait to go over everything on the bike once again. Checked all the electrics and the carb for the thousandth time. Still nothing. Decided to pull off the flywheel... Everything OK. Timing: OK. Took the cylinder off and found a nice surprise! Both rings on my brand new S3 piston tightened up and got stuck in the ring groove. It's a mystery to me why, as they were gapped to .30 mm and were installed the right way up. Maybe the oil (which i put there 7 months ago) gummed up and made them stick?

anyway, cleaned them up, put everything back together and now she's a first kick starter. Loving life again!

Thanks for all the great advice people, it's been a real adventure!

Hooray lol