Bisson Sport Strap-on Muffler
Omega 15%
OS #8 Plug
APC 12x4
Peak 13600 RPM
Measured thrust: 7.8 lb.

The Bisson Sport Strap-on Muffler sounds like a tuned muffler. I think 12x4 is too big for this muffler, as it will not slow down no matter how rich I adjust the hi-speed needle. Perpahs it does not give enough back pressure; yet it does not lean out when I hold the plane vertical. I shall try APC 11.5x4 and see what happens.