Starts good cold...won't re-start after warm. Has good spark.

Tim

 

check compression. make sure vent lines arent plugged or pinched.

 

you could also have a leak some where. everything is air tight when cold but after the cases start to warm up and expand it creates gaps. not a big problem if seals are still pliable but old seals will not handle this very well. after you get it running and warmed up try spraying carb cleaner around all gasket areas, intake boots and exhaust manifold if you notice an increase in RPM's then you have found an air leak