Vespa 90 Driving me nuts

Starts fine when cold. Slight sputter on top end.  Shut off warm (plug temp 135F)  wont start. Engine completely rebuilt 8-10 yrs ago.  Compression nearly same warm and cold approx 120psi, dellorto 19 rebuilt, tank cleaned, points and timing good, nice blue spark, Runs like a top, I just can't shut it off unless I'm staying long enough for it to cool down about 30 degrees.......

Hi I had a problem like that and it turned out to be the condenser had a internal sort that only showed when hot and it was a pain if you stalled it in traffic no way would it restart the spark went weak when hot so no go it showed when we had a dwell meter on it the dwell changed as the engine heated up

 

Good luck Clayton

 

hi

some years ago i had same problem, solution change ignition.