something to do with something being stuck. not much help I know, tap it with hammer, gently, and hopefully it will free up. I think its the float? not sitting correct. Mine did it a while back, just the 1. tap tap, no problem
It's the shut off valve in the floatbowl, as said just tap gently with something to free it.
The rising fuel should push it shut but sometimes thay dry out and stick if you've been running on gas for instance.
If hitting it with a hammer doesn't work.....................
.................you will have to remove the carb, remove the bottom cover plate and adjust the brass tab on the float hinge. If you have to go to that trouble it would be worth replacing the shut off valve and the o ring seal on the bottom cover plate anyway.