Stuck Heat Riser

jhdeval said

Okay now that I have the exhaust apart I can see the heat riser is mostly open. I have instructions for removing the counter weight etc on the outside but can you remove the plate and pin?

I would like to keep it but obviously it needs to be removed and at least cleaned to make it operate.

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There is a bimetalic spring on the shaft of the heat riser (unless it fell off), so when the engine is cold the counterweight keeps the plate closed. Or they use either a spring or the counterweight, can't remember. Either way when you start the engine the exhaust gases are now forced to go through ports in the head to a chamber beneath the carb. This heats the incoming mixture until the exhaust manifold gets hot enough that the valve now opens. Unless you live in subzero temperature in the winter and drive it in the winter it's not needed. Yes remove the plate but keep the pin or you'll have an exhaust leak.