This is my 1st OS engine, I have broken it in the way the manual says...I have got my starter problem solved thanks to you guys!! My next qeustions is this...how do you know if your engine is running too hot? I just ran it in the yard, first it would crank up.....but when you gave it throttle is stalled out...assume it was running to rich...leaned it out just a couple of clicks and it ran fine.., ran it approx 4-5 minutes....it just seemed to be awful hot...just wondering if thats normal? I have been running super tigre .27 engines and run them hard and they dont seem to be as hot as the OS 75ax. Btw this is on a airboat...figured you plane guys knew these engines inside and out.