503 Throttle Problem
in 2 Stroke Technical Questions
7 years ago
I have a problem with my Rotax 503, (dual carburetors, dual Ducati ignition). The Bing 54 carburetors are set up per the manual. Idle is about 2100 rpm. It's in a pusher configuration on my Chinook Plus II. When I advance the throttle from idle, the engine hesitates / stumbles and then catches up and runs fine in the mid and high ranges. When I close the throttle, bringing it back to idle the rpm drops 300-400rpm below the set idle speed and then slowly returns to 2100. Because this causes the engine to run very rough I often have to open the throttle slightly to get it back to the set idle speed. Does anyone have a clue as to what's going on? I've about run out of ideas, having rebuilt and re-tuned the carburetors trying richer and leaner e-clip settings for the needles as well as larger (50) and smaller (40) idle jets.
