If you look at the really great Lugnutz video he did, this riser is a primitive, iffy feature. Due to convection and conduction and the fact that heat rises, in my opinion, there is not enough difference in open and closed. There are thousands of stuck open and stuck closed risers across America. Nothing horrible is happening. So if I had this I would cut it off until a better solution is found $600 plus dollars later. I believe there could be an insulator under carb. All those castings will be real hot, eventually, no matter the riser. Too much false science is being placed on a low tech flapper. Have not seen documented facts to support faulty heat riser serious motor damage. Just hearsay speculation. The poster has not reported any performance issues with the motor.
If I have to agree, I agree with Carl that stuck closed is better. If closed means flapper diverting to tail pipe.
I do see a semantics issue here. I myself was confused until I saw the Lugnuts video. Open/closed can be seen differently. I am taking the road that, at rest/cold, the flapper is open, letting the exhaust blow on the bottom of the intake. Then when the bimetal spring gets hot, it sort of "closes" off or diverts the flow down toward tail pipe.
Tom, view this and see if your explanation is OK.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
