Ok, just with what you have said, about your plane I could not even begin to think what is wrong with your engine. you need to describe engines problem in detail with symptoms the engine is currently exhibiting and what exactly have you done to correct the problem, your solutions may have aggrievate the problem.

Just from my extensive knowledge of Alpha and Arrow trainers, and the Evolution engine, check to make sure the fuel feeds from the tank and the small section between the remote needle assembly and the fuel inlet are not knicked and the same with the pressure line between the exhaust and the tank. I am one of three instructors at our field and in 8 out of 10 times, I have found these knicked and had to replace them. Also give your plane a hard jolt see if your clunk is in the right direction it may have curled forward if it was left on its nose for a while.

Other than that you have not informed us in the peanut gallery as to what the engine does, does it idle smoothly, does it burble at idle, is your high end idle too lean, causing your engine to heat up and lock up? If it has had a lean run and gotten hot, your glow plug may act like its good until it heats up and then loses its reaction and kills your engine. You have to give us more information to help you out!!!!! Has it acted like this from day one or have you had any good flights?

will