I got to break mine in and run it for the first time this past weekend. Mine ran great. Odonnell plug, JP6 pipe and TQ 30% fuel. It had an excellent idle (probably the best of any engine I've owned), that will idle FOREVER... And no one pulled me down the straights. It does have more of a mellow tone at full throttle which could trick anyone into believing that it doesn't wind out. I honestly believe that engines are one of those things that you can't make a purchase on by just listening to what others have to say. I use to run O.S. engines all the time. I bought a V-spec and ran it for 10 gallons before taking it out of my buggy. I took it out because I knew that it was getting about time to go through it. It could have possibly went another 10 gallons. I never had to do any work or replace any internals on it. On the other hand, at the same time I had my V-spec every one's posting about how bearings will not last more than a gallon and they're breaking rods and it's junk, blah... blah.. blah. My point is, everyone breaks engines in differently. People run different types of fuel. People oil their filters differently. People run different pipes. People run different gearing. People have different driving styles. I could go on and on... However I do believe that anyone can get an occasional lemon. I had a plus4 and was not impressed with it at all, some people love'em and that's all they will run. I'm not gonna bash it. Maybe during break in I did something wrong. Maybe I ran it too hot. It's money I've spent so I'll probably rebuild it and try again. If it has problems the next go around then I'll make a conclusion on it's quality. Mr. Howart has been on this thread and posted that they (Reedy,Associated) would stand behind their product. That means allot to me as a consumer. With an O.S. once you bought it, it's yours. Didn't run right out of the box...oh well. But they state that when you inquire about any warranty. High end O.S.'s have no warranty. That's not bashing O.S., it's just the facts. All in all, the 121 is a great engine. Mine runs great. I wouldn't hesitate buying another. (When I save up again)