Ace, you don't want to run that engine above 300-320 degrees... 280-290 would be in the normal range... but having said that, raising the operating temperature of the engine a few degrees, isn't going to change what is happening in the exhaust system... as you already know a four stroke only produces an exhaust pulse every 720 degrees of rotation; where as a two stroke is every 360 degrees of rotation, so a two stoke produces a hotter exhaust than a four stroke.

What I think is happening, is the exhaust system is cooling off by the airflow through the cowling, since the exhaust system doesn't have a lot of metal mass to hold on to the heat... you can try a couple things, like baffling to keep the airflow off the exhaust system... the other thing you can do, basically what the performances engine builders use to do (and are still doing) when running thin walled tube exhaust headers... was to raise the temperature of the exhaust gasses inside the headers to increase the gas velocity by wrapping the exhaust headers in a fiberglass thermal wrap.... the fiberglass wrap insulated the exhaust header tubes and kept the heat from dispersing through the thin walled exhaust tubes.

If you were to wrap the entire exhaust system from the head all the way to the end, except the tips sticking out the cowl with a thick strip of heavy fiberglass, overlapping each wrap as you go, and then secure it with some wire at each end, that along with a baffle to keep the airflow off the exhaust headers would help hold the heat in the exhaust system... its worth a try anyways.

Cut a strip of fiberglass and fold it over in half so the frayed edges meet so when you wrap it around the exhaust tubes. the overlap will hide the frayed edge... wrap it tight!



John M,