ORIGINAL: jimcork1
ORIGINAL: tkg
Back to basics..... Remove the carb, check that the buttery is installed correctly. The butterfly is NOT round but oval and has beveled edges for correct sealing at low speed operation. Unscrew the idle speed screw untill the throttle arm does not touch. Hold carb up to sun and see if any light leaks past the butteryfly, light leaks = air leaks = fast idle.
Ok I went back to basics. Pulled carb closed butterfly fully and no light passed around the edges. There are 2 notches and 1 lines up exactly with the low speed fuel inlet. So my assumption is the air through this notch is what draws the fuel at low speed idle. "if it had an idle"
So on with the rubber replacement and more testing. If this doesn't work,, new carb will have to be next, or replace engine.
I am sorry to ask a few more questions from you, if you don’t mind?. Does your throttle arm rotate a full 180 degrees or just 90 degrees? Did you bought this engine used or brand new? Has this engine ever run O.K. before?
I am very intrigued with your problem and will like to help if possible.