Paul,


I believe PropTop was referring to the piston-baffle; not to one in the muffler.

The BlackHead and the Silver Line series engines both had a baffle/deflector on top of the piston, on the intake side.
It is required to prevent freshly inducted mixture from just flowing straight out of the exhaust.

The Speed uses a flat-top piston and angled schnürle ports, which achieve the same purpose even better.