RE: WHAT A DEAL
MB 290 25cc prop data.
16x8 MA 6500 ---- Box stock except for spark arrestor screen.
16x8 MA 6700/6800 ---- Remove exhaust deflector and packing in muffler.
16x8 MA 7300 ---- ST 2000 muffler.
It appears that most any exhaust change improves RPM considerably.
ST sure does make ugly mufflers. However the muffler to engine adaptor should work with a tuned pipe.
Bill