For what it's worth: I fought with this engine for an entire season and could not get it to run properly; I even sent it to Horizon to have the pump checked out. I finally installed a Perry pump and the engine was immediately easy to operate and it runs fine; very predictable. This is the fourth year I've had it and it has had one bearing change, over 350 flights with no major problems. (I did have a hard time diagnosing the problem when the bearing went bad.) (Mueller header/Grieve pipe.)