[maxhifi]

Stalling under load sure sounds like a fuel delivery problem. First make sure you're getting adequate fuel pressure to carb (I've done this by pulling HV wire off centre of ignition coil, disconnecting carb from fuel pump, putting thumb over end of fuel line and getting someone to crank engine.. It should build up a lot of pressure like a garden hose... Be careful if you do it this way though!!!) then check carb for proper operation and adjustment. Also, if you haven't recently, verify ignition timing. Actually maybe do that first since it's easy.