OK, I have 2005 Evin ficht 150. I really like the motor. The problem I'm having is that when running at wot, the motor seems to loose power and slow down. It acts like its running out of fuel. The length of time it takes to happen can very between 5-20 min. and doesn't happen every time. I've put in new plugs, fuel filter, and check valve in the tank. Didn't seem to help. Any thoughts on this?