Originally Posted by doki_doki

well, with my experience with os engines, they are very durable. with the right break-in method and tuning you can let these motors run up to about 60 liters without changing anything except for the glow plug i know someone who ran the ostz 5ports up to more than 60 liters until the engine finally broke down. the piston was broken. we also noticed that there was a noticeable play between the conrod and crankshaft pin... and we quessed that caused the failure...