I am finishing rebuilding my carbs but before I lock down the throttle shaft screws, I want to make sure that I have the butterfly valve adjusted correctly. The only advice that I can find on this is to shine a light from behind and adjust it until the least amount of light is showing. Can anyone recommend a more technical adjustment or verification method? I don't want to peen the screws and then find that I did it incorrectly...
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Re: How to align butterfly valve on bing rebuild
by Roger Lee » 7 years ago
Nothing special or hard to do here. First make sure the center punch mark on the brass butterfly is at the top and facing outward. The with the screws slightly lose close the butterfly and move it around so it looks like a good seal all the way around. If you see any tiny gap slightly open it again and move it around so it seats perfectly all around. Then tighten and peen the screws over.
I use a 1 3/8" piece of aluminum rod 6" long. I clamp that in the vice pointing up. This rod is the perfect size for the throat of the carb. With the butterfly closed I slide the carb down over the rod and allow the head of the screws and the butterfly bar rest on top of the bar face. Then you can take a flat headed punch on top of each screw and give it a few taps with a hammer. They will never come out unless you grind or file the screws off so no worry about them coming lose and going through the engine.
Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell
Thank you said by: Kyle S, RotaxOwner Admin
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