This is what mine does as well. Only time it doesn't stall at stopping, is if I have the idle set high, or if I put it in "N" and keep my foot on the gas and the brake. Everyone told me it was a vacuum leak. I replaced the carb gasket, found a line with a hole it in, still same issue. Driving down the road it hesitates unless my foot is on the gas, press in the clutch, and it smooths out. Mainly at 5-50mph. I think mine has a vacuum leak at the throttle butterfly shaft. When we took the carb off, it was all black by the spring.

Guess it is time for a new carb. I bought a new PVC (mine was clogged), no change. I also got a fuel filter, haven't replaced that yet, it is next.