ORIGINAL: ChuckW
One quick and free thing to do is remove the baffle from the muffler and drill out the muffler outlet.
And upgrade the bearings..... I had an early AX and the bearings didn't last anywhere near as long as a cheaper Chinese engine (same prop, plane, and flying hours).
I'm not knocking the AX engine but the narrow rear bearing won't last quite as long as the wider bearings used in pre-AX models.....at least that's my experience.