RE: OS engines users Club
C., I remember Harry Lagman I believe saying that the exhaust pipe can be changed to one with a larger inside diameter for a power increase. Maybe he will read this and reply. I think the Surpass doesn't respond to 20% and 30% nitro like some of the other 4 strokes. I'm just going by what I have read here at RCU; never tried more than 15% nitro in my O.S. thumpers or the 2 banger.