Thats the indications In my view. . There's no obstruction to the flow of cooling air. It will go all day at part throttle. . Considerable reduction of pressure at that setting. It's my sons. I can't waste any more time on it.. Another thing with four strokes they rust up exhaust valve guides. You need to squirt CRC down the muffler about 10 mins after stopping the engine to prevent that. Nev