I've been running a GMS .25 on a Dogfighter for about a year.

I've had and solved the usual problems.... air leaks around the carb etc. and have had an excellent running engine. Even shuts off via the throttle! (I know, they should all do that, but the GMS's that I've got all need a few leaks plugged before they do.)

Last weekend, after a mid-air, my dogfighter went in pretty hard. I managed to shut down the engine before it went in, so the carb was closed on impact. Everything seemed OK, no significant amount of dirt in the carb. I cleaned it all up, replumbed the fuel line that was severed in the crash and started the engine.

Everything seemed OK, but after about 5 minutes in the air, the engine started losing power and eventually quit.

Back on the ground, I could not get it to run above an idle. As soon as I opened the throttle, it leaned out and quit. I removed the needle and pumped some fuel through the carb to blow out the seat. It seems clear, but still won't run above an idle.

Finally, as a last resort, I put a longer tube on the pressure line and blew into it while I ran the engine. Now that the tank is somewhat pressurized, the engine will run fine. It seems like it just doesn't have enough draw to pull the fuel in.

Whats Up??? Is it possible that I've ingested too much dirt and the engine is too loose? It seems like it's got the same compression as it always has. Could there be another air leak somewhere else that I haven't found? What would cause it to lean out when the throttle opens? I can crank the needle valve almost out with the same results.


Thanks for any help.

Sounds like an air leak or a cut fuel line. Did you check the clunk? May have come forward in the tank in the crash. Just a few thoughts.

Thanks for everyone's help.

Problem solved.

How did you solve it?