Erratic running at low RPM

I'm troubleshooting this motobecane and I was hoping to get some input from you guys.

i installed a stock Av10 cdi kit on to a AV7. I used a modified points magneto nut and an AV7 points crank. The rest of the engine is a Parma 70 with 19mm PHBG, air filter is malossi horn 90 degree, and the pipe is a Doppler. Timing mark on rotor passes the timing mark on the stator at 1.5mm BTDC, just like my other cdi setup. CDi box is from a yamaha jog.

So the spark looks good, carb is clean and new, compression great engine just rebuilt, yadadada. When I try to start it by running it along the ground, it will quickly fire, but not every revolution, maybe three at a time, then four off, then 6 fires, then two off, etc. if you can push/coast up to about ten mph, it will usally get going, and blast along to top speed. once it goes fast enough, it runs pefectly. great throttle response, no dead spots, hard acceleration.

But when you slow down, it almost completely dies and no amount of revving or throttle will keep it going.

seems like a timing issue? Or could it be a bizarre carburetion issue? the idle jet is definitely too rich, being the stock 50 or 55. And if the auto advance was moving the timing mark, i don't see how that could cause erratic running.

Any ideas?

Re: Erratic running at low RPM

def. timing. getting that CDI spot on with a points crank is tough, are you using a dial indicator?

Re: Erratic running at low RPM

Nah, i just eyeball with a upside down spark plug, like everything else. I guess I'll have to get a little more exact.

Did i ever mention how lazy a tuner I am?

Re: Erratic running at low RPM

A cheap timing light is good for getting that right but whats wrong could be so many things. You could have someone crank it over as you observe the spark to see if it is erratic

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