Thanks for all of your replies. Good thought
Tiny however I have not had the hand throttle connected for many years. The return spring seems fine and looking down the venturi when the engine is cool, I don't see that the throttle plate is stuck open, though it does have a little 1mm or less gap when shut.
4ontheFloor , I still have the phenolic spacer. I have not tried to shut it off and start it up again when it is hot so I will have to try that. It's just fine on a cold start though.
atomarc , I have thought about the throttle plate hanging and the throttle shaft is undoubtedly worn to some degree from age but I have gently stomped the gas pedal to see if that would kick it down but no it doesn't. Thanks for the ideas and I'll keep checking these things.
littlebuddie
