Hi everybody,

I would think that if you are running the engine super rich, it has an exaggerated cooling effect. Therefore, since the sleeve is tapered at the top and you are running the engine in a four-stroke fashion, then you might not be getting enough heating of the upper sleeve to prevent the top of the piston head from slamming against the tapered end of the sleeve and prematurely wearing it out. The engine will break in but at what possible cost, reduced engine life? But, I will freely admit that if the engine gets hot enough by following the method in the manual to allow proper expansion of the sleeve, then I withdrawl my statement about the break-in method. Though, I think if you google it, more people would say not to break in an ABC engine by running it super rich. I remember when I got my 55ax (the first I bought - have a .46ax and 75ax also) it was extremely difficult to turn. I had to heat the cylinder head to get it to turn easier. Why, because of the piston head hitting the tapered sleeve. I am one that believes that the OS AX series of engines are good enough to be able to slap them on a plane, run a tank through it and start flying. I do think that after a gallon of fuel, it should be broken in unless he is not stressing the engine enough - really running it rich. Does anybody here agree that the 55AX should be ripping the Kaos all over the sky? Also, he never stated what he wants exactly, more speed or more power (for vertical). Has anybody looked at what prop size an OS 75AX engine will turn. The 55AX manual is stating that it will turn the same prop that the 75AX will. Does anybody find that odd or a little hard to believe? At what rpms does an engine usually produce it most power? At what rmps is the 55ax going to turn a 13-7 at (it being stock of course - no pipes)? Will it swing it at 12000-13000 rmps? I can tell you from tach readings, it will not. Of course, your mileage may vary. But again, I am not saying that it is impossible after some use / lots of flight as I only have 15 tanks through the engine. If it does, then I, Iluvflying and anybody else who has bought this excellant engine are in for a real treat.

Happy Flying!