[deckeda]

1) I replaced the CDI because it was cheap and because everything else in the ignition system checked out good.

2) I have the gas tank bypassed with a temporary one.

3) I rebuilt the carb. It would start better and rev but really only on choke and with the mixture set rich. I could get it to idle and run off choke eventually. But, it would backfire though the carb as if it were lean.

But it still woudln't start hot, so next I looked at valve clearance.

4) Both were tight and I set them towards the greater end.

intake = .006-.008 and I set it at a snug .008
exhaust = .007-.009 and I set it at a snug .009

Bike would run maybe a little more smoothly but still only when rich and only when on choke. I slowly moved it off choke and it would run but at a reduced RPM, as before. I didn't get popping any more, so I guess by valve adjustment fixed that.

I readjusted the mixture to about 1 1/2 turns out -- what Kawa recommends -- and it only runs for about 2 seconds now. I don't know what else to check.

 

[deckeda]

It's astonishing how many little things can go wrong with such a simple 1 cylinder engine.

I read that if someone had previously turned the air/fuel mixture screw too far in when resetting it, that its needle could snap off and be forever jammed in the carb, ruining it and causing a similar issue: only runs at idle with choke and won't run off idle.

I just looked at the old mixture needle screw and it's fine. So that didn't happen here. And besides, earlier I had run the screw out to make it richer and that worked for a little while. So I know the mixture screw is working.

I'll order a cheap ignition coil next. Not because I have any reason to believe the original is bad -- I tested it -- but at this point I've done all the regular diagnosing and I'm just swapping out parts because money grows on trees and time is infinite.

Next up will be a cheap carb, however I know enough from research to open them up first and verify the jets are the correct size.

Not too much left, unless I want another go at the valve clearances ... I read that that a bad voltage regulator will freak out a CDI and cause it to not send signal to the coil. This regulator never goes beyond 14v at higher revs, so that's also "good."

Hmm, what else ... maybe somehow there's a huge gash in the manifold/carb gasket thing, slurping in so much air it only runs on choke and so on. Maybe I just order one of those too. Or maybe I'll stuff the engine full of twenties and call it a day. Seems to have the same effect.