Blocked primary jet? Try purging the carb by cupping a hand over the throats while it's running. If you can get it to pick up fuel then hit the throttle and try purging it again. The accelerator enrichment jet is easy to check and doesn't require the engine to be running to test it - hold the choke butterfly out of the way, open and close the throttle quickly by hand and you should be able to see and even hear the fuel squirting from the jet in the side of the primary throat. No shot of fuel = damaged diaphragm in the pump.