If your radiator is full and you have the correct 4psi radiator cap on it and it isn't boiling over, it's probably not overheating.
You definitely need to fix that heat riser valve, though. New springs are available if yours isn't any good.
Even if the engine isn't overheating per se, the heat riser could be stuck in such a position as to direct too much heat to the base of the carburetor causing the fuel to be vaporized before it gets to the combustion chamber.
Last edited by Otto Skorzeny; 09/14/2022 2:01 AM.