Hi Malc,
Mine did the same thing after the carb had been stood with no fuel in for 6 months. Could be dirt in the jet or, more likely, there is a small ball valve in the accelerator pump on the carb which sticks as it gets clogged up with residue. This usually clears when fresh petrol gets through, but when it does stick, it means that if you put your foot sharply on the accelerator the engine can die as there isn't enough fuel and too much air.
See you at Stanford 😃 😃
John