I had the opportunity to assist in the teardown and inspection of my old motor. 12A. It failed during its' 5th season. 3 years for me, 2 years for its' current owner.

Other than the obvious "rebuild after 4 seasons" what could have been done differently?

The front rotor broke an apex seal in half. The rear rotor broke a rotor at the apex seal groove. One of the rotor housings had a crack about 1/2" long from the leading sparkplug hole.

Is this a result of detonation? Was their too much clearance between the apex seal and its' groove? Insufficeint oil in the fuel? Too many rpms? What?