So, I rebuilt a guy's Lawn Boy 10201 V-series...(I know, that was the first mistake). New piston & rings, new main bearings, new seals, etc. I was getting it adjusted and broken in and suddenly "SQUEAK...BANG"...No power. Not good. The rope wouldn't pull and you can barely turn the engine over from the blade end. I pulled the spark plug to look in the hole and what I found is ugly. There is a huge gash in the bore from the intake port up about 1/16" deep and at least an inch long. It looks like a piece of the top ring broke off and got jammed between the piston and the bore...probably what the squeaking noise was. I sent a message to the company I got the piston and rings from. Maybe they had a bad batch. Most likely they will tell me that I broke it. So now, I am stuck replacing at least the block to get this guy's mower back to him. Anyone have a good V-series block they want to donate???