Never had any problems with mine until I dented the piston trying to get the crank nut off. Now I am just going to get a new YS80, since it is only about 125.00 more than fixing the YS61 that I have right now. I ran many many gallons through it with no trouble. It was hard to start the first flight of the day, but after that it ticked right over. And having to switch back to the OS61 I can verify that the YS61 make much more power.