engine sputtering

[LapTraffic]

Went riding in some hellaciously muddy conditions last weekend and my friend's 400 is not running well afterwards.

He has a K&N with outerwears and hole in the lid. There was a very small amount of water in the airbox, filter looked fine.

I'm wondering if this could be a rev limiter issue? My wife's warrior acted up in a similar fashion. I just dont know much about 400's

When he gets on the gas it wants to cut out. Lot of popping and sputtering and hesitates quite a bit.

Any ideas on where to be looking? Wet plug?

Thanks for any help!

[gojk]

Pull the boot goin to the carb and see if there is any dirt in there. IF there is I would pull the carb and tear it apart and clean it out.