My engine starts on the second kick when cold, but after about a 15 minute ride the engine won't start if I turn it off and try to restart. If I wait for the engine to cool it then starts again on the second kick. The clip below is trying to start the engine after about a 15 minute ride. The engine turns for a few seconds but does not respond to the throttle (even WOT) and then dies.
The hot start problem has occurred as a result of me splitting the cases to change the clutch and fly side seals. When the barrel was off I sent it (together with piston and rings) to our local Vespa mechanic. He 'measured' everything up and he said all was within tolerance. He did hone the barrel as there was a small scuff mark below the exhaust port. The scuff has been there for a while as I remember seeing it the previous time I removed the barrel. After getting the barrel back from the mechanic I re-assembled everything and starting experiencing the hot start problem.
I noticed an oily leak on one side of the head and I subsequently pulled the barrel again to lap them. Before I put the barrel back I measured the following;
ring gap between 0.5 and 0,55mm.
squish clearance +- 2mm using the solder wire method
piston oversize 66.9mm.
I put the barrel and head back and no longer have the leak but still have the hot start probem. I measured compression at around 100 psi with a warm engine (I can't remember what my compression was before the hone but it has never been good)
I know that the measured figures are not great but the bike ran extremely well before I decided to do the preventative maintenance and change the seals. The bike now also bogs slightly for 1 or 2 seconds and about ΒΌ throttle but disappears as the revs build. I find this strange as I left the carb intact when splitting the cases.
Hoping someone can give me some direction on how to solve the hot start problem.