If this is a new phenomenon, then I would check my float needle for wear at the tip, debris, or a build-up of deposits on the seat, or replace the float needle.
If this has been going on for a while, or you are unsure, then I would at least check the float height. If this is the trouble, then it is also dumping your fuel on the ground when landing from jumps, and any hard impacts.
Good luck!
Jim Cook
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