OS 91 FX in Shoestring Racer
Cyclic Hardover,
I wouldn't want to hack on O.S. for this problem until I tried to run it with the stock muffler....which is an excellent point that someone in either this or another thread made. I never did run the engine with the stock muffler. I believe that this problem was due to the aftermarket Pitt's muffler not supplying enough pressure to the tank. When I ran it with the muffler the first time I could all but remove the needle valve and it would keep on running. The engine would never richen up and die as it should have. Then I plugged one of the muffler exits and it improved but the needle still was too far open for a typical OS engine telling me it was still starving for fuel. Realizing that increasingly restricting the exhaust exit will actually worsen the overheating problem my only possible solutions were to put the stock muffler on and hack up the plane to make it fit or to install a pump. The pump seems to be working great and has thus far eliminated the overheating problem. Unfortunately, I purchased this motor before I found this site as I'm sure I would have opted for something else considering all of the problems reported here. I've also had it too long before using it to even think of returning it so finding a solution was necessary.
Jeff