I have had two ASP .40's and loved them both. When they start to flame out in climbing or inverted flight after hundreds of flights , it may be that the cylinder/piston fit is too loose causing reduced fuel draw. If your tired ASP has nil compression after running and is really hard to re-start, this is a clue. Of course check for air leaks in fuel lines, carb O-rings, etc,etc. With this cheap an engine, it is probably wiser to buy a complete new engine than to replace a worn cylinder and piston. I read somewhere that the ABC type engines are not happy with running slow/ rich for extended perods of time and that this prematurely wears piston fit. The opposite is really dumb, don't try to fly an engine set for max rpm on the ground with a big prop and expect it to last. Find an experienced somebody who knows how to set high and low needles (before you fly) if you are not sure how.

BTW, Which US supplier sells ASP engines now?