It is probably the float valve/needle valve. the petrol leaks through, overfills the float chamber and runs back into the sump through the breather pipe.
To fix it, take off the float bowl then pull the pivot pin out from the float so that it falls off the carb. Shake it to make sure that it is sound. You should see a pointed bit about 1/2 inch long loosly fixed to the float. If there is a shoulder on the point, put it in a drill and spin it whilst smoothing it off with a bit of emery cloth. If it is a rubber point or the point is good, get an ear hole cleaning bud with some metal polish or fine grinding paste on it, slide it up the hole that the pointy bit came out fom and spin it. This will clean up the seating. When you put it back together try sucking on the petrol pipe leading into the carb. If it holds a vacuum ie your tongue sticks to it, you have fixed the problem.
podgyoldgit, June 2010
