i am trying to make my 250ex faster but still fun to mess around with and im wondering what kind of air filter would be good and if it should be with a lid or not because i might go through shallow water or mud puddles every once in a while

 

UNI foam air filter, comes with a different wire insert than stock. It is way less restrictive and flows a lot more air. Be wise and stay away from K&N, it will pass dirt!

As for the airbox lid, why ask us when that is something you have to decide for yourself based on your own riding conditions? If you decide to go wide open, be aware that the little 250 engine can only handle so much air. You open it up wide, and you can get so much air that it will never jet properly! If you decide to go partially open, try a few round UNI airbox vents or an EHS Racing Outerwears lid.

Any mods to the air intake or exhaust are going to require a rejet!

 

I added 6 Uni vents to the lid of mine and it worked out great. You still get the mud protection but the benifit of getting more air. Just remember to bump up your main jet to a 110 or 112 and it will run great. 250ex is is one of the best all around do everything, with little maintiance atv.You should also bump up the pilot one or two sizes.
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