Bad By-starter?

[agostini]

My '84 Aero 50 (NB50M).

Sometimes will start, sometimes only after LOTS of cranking, sometimes starts and briefly runs then dies and won't start. Once running and warmed up, it runs great and can be shut down and restarted with no problem.

Has new: CDI unit, gas lines, rebuilt carb (original I believe), gas and air filter, and re-sealed gas tank.

When not starting, gas is getting to the carb (tested at float bowl drain screw). Getting good spark at the spark plug.

By-starter tests good (continuity), and when attached directly to the battery for 10 minutes, it extends about 2mm.

Wouldn't start this morning so I removed the by-starter - fired-up immediately. Once running, it started to die so I put my thumb over the orifice where the by-starter would screw into the carb and it would run again. To keep it running while warming up, I had to modulate my thumb over the orifice, letting some air in and then blocking it off. Once warmed-up, I installed the by-starter - it ran GREAT. Spent the morning running the scoot around town - could stop and restart no problem - flawless...

I'm wondering if the by-starter is not retracting enough when cold, thereby not allowing a rich enough mixture at starting.

Thoughts? Guesses?

[martynkim]

Sounds right to me. I have one if you need one.