I recently took out a G20 powered model that had not been flown in about five months and decided to give the engine a run before taking it to the flying field the following day. The engine started up as usual but would not go past a fast idle and any attempt to incresase the throttle resulted in very raggedy running or an abrupt shut down. I drained the tank of the old fuel that was left in in from the last flying day and used fresh fuel, but still no go.

I inspected the carb, and though finding nothing out of place dismantled it and replaced all gaskets and diaphrams but still no better. I checked the ignition system complete and found no problems there. Looking through the fuel system showed nothing amiss ,but on a whim I tried blowing through the carb's feed line and felt clunk and found it extremely difficult to do.

So after two full weeks of hair pulling and head scratching it turned out that a partially clogged felt filtered clunk was the culprit.

Karol