I have one of these engines. Because it is a ringed engine, it took a couple-three gallons of fuel to break in. Not your typical ABC(N) break in. It ran good until about 8 gallons of fuel, then the rear bearing became noisy and went out. I replaced both bearings, front and rear, from Boca Bearings. I have run at least 10 gallons through it since then and it is a very strong engine. I use an APC 12x5 prop on a GP Ultimate Biplane and it just screams. Best engine I have.

The factory bearings should have lasted much longer than they did, but sometimes a manufacturer just gets bad parts. I believe this is the case with the factory bearings. I couldn't be happier with this engine now...

For what it's worth.

Oly