Stock air filter

[2001 trx400ex]

Has anyone taken out the metal core inside the stock filter and ran it with just the foam. I had a K$N but i sold it cuz i didnt like it. I put the stock on with the core out and i didnt find any difference in performance.

[Sportrax10]

I think thats just for keeping the foam sturdy. It probably dosnt restrict enough air to add performance when you take it out.

[2001 trx400ex]

y did i notice 0 difference between a stock air filter and a K&N. K$N says they give 2 more horsepower. I got a pipe rev kit and hotcam stage 1 and no choke. I didnt notice any difference. jets r 165 main and 45 pilot.

[400extracc]

u say'n u have a pipe, cam, filter, and no choke and u feel nothing. whats up with that??? all i have is a t-4 slip on pipe stock filter with air box mods. and jetting, i feel a difference. a pritty good difference. its all in the jetting man. wrong jetting u'r quad will run like crap. just from what i have noticed with poor jetting.:macho

[2001 trx400ex]

i didnt notice any difference when swapping the stock filter wth the K&N

[2001 trx400ex]

help please, is this good or bad to do.