I also posted this to the Quadra support forum.

My Q100 started running very fast with the throttle closed and I had to run the airplane out of gas in the air to get it down . Naturally I thought it was a throttle linkage problem, but the linkage was fine and throttle butterfly was closing completely. I took the carb apart, cleaned it with carb cleaner, reassembled it, and it still does the same thing. Putting a different carb (Wallbro SDC80) on it solved the problem.

I called Bennett and they said to look for wear on the butterfly due to vibration - but there is none. The butterfly closes completely.

Any ideas? I guess I'll send the carb away for a rebuild.

Mark

The wear that Bennet was talking about is where the butterfly goes through the shaft. Vibration will cause the shaft to oscillate end ways wearing the butterfly at the shaft, butterfly joint, but it takes a long time to wear. If the cut return spring is still on it would unlikely wear, as it is there to dampen the vibration. Is the idle stop screw removed ?

I took a look at the butterfly, and the screw that holds it to the shaft had come loose. I tightened it up with some red locktite so we'll see if that was the problem.

It's amazing how things come apart on these paint-shaker motors. One time I found that the whole cylinder had come loose from the crankcase. You have to check and locktite everything on a regular basis or it just shakes apart.

Thanks,

Mark