After it sits for a few days pop off the air cleaner lid, and look down the carb while 'pumping' the throttle by hand. If you see no fuel squirting out of the accelerator pump nozzles your carb is either leaking fuel out of the bowls, or more likely the fuel is evaporating out of the bowls after sitting a few days. Each time you pump it by hand while watching you should see a healthy shot of fuel shooting out of the those nozzles.

If there is a lot of fuel shooting out on each pump your problem could be either a weak spark or an incorrectly adjusted choke.