Well, I learned a hard lesson about rebuilding a WB2 carburator. Don't always trust the exploded view of a carb etc.
This particular carb was on a Homelite Super 650. I battled with this carb/saw for about a year now. Finally, I figured out the problem.
My guess is someone did an incorrect rebuild in the past. I tried to do a rebuild and duplicate the parts but the parts were wrong.
Well, the problem was on the metering side under the circuit plate. The Homelite IPL's of the WB2 carb showed no diaphragm on a 650 and a check valve diaphragm on a super 650 under the circuit plate.
Well, in short, you have to use the gasket with the slot and a hole on each end toward the carb body and the diaphragm with the check valve flap above it toward the circuit plate. Doesn't seem to make sense but it works.
Hope this corrects or save someone else a major headache......J