Drain your tank, when you run rangers in water and mud the vent tube can let dirt/water/silt in. Try cleaning out the tank and spray out your fuel pump with carb cleaner.
I had the same problem and this fixed it. I did find silt in the tank and the vent tube was very dirty on the inside, I actually put a filter on the tube to prevent it from happening again. Hope this helps you.
07 TLD
Stock Bore/Stock Stroke
With a few trick items
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Our Drinking team has a Racing problem! lol