Hello all well I think I trashed my os .91FX, I run to small of a prop on it and over done it. I had mounted a 13-4 on it hoping to get more tork out of it and I did for the short flight that it lasted, my fault all the way. So my question is what can I do to salvage it? new sleve? new piston? or could have the block warped aswell? Ive never done this so its a tough pill to swallow. I putt a larger prop on it and run it in the test tsand but it wont run but just a minute then if I try to advance the trottle it just knocks and dies plus it gets hotter than hell in that short run time. All most looks like a parts engine at this point.