i put a 155 main jet in and modified the air box. U know the 2 clips in the middle? well take the lid off and stap those 2 middle clips down, put the lid back on. The 2 metal clips towards the back, snap those and leave the front clips off. THis will give you all the air u need. Gas it in 3rd now and front in will fly up

 

btw, a jet runs at about $2.99 at any atv supply store. Just take the bowl off from the bottom of the carb, (its 17mm im pretty sure). Make sure u turn the gas off and leak the remainin gas out of the lines. Take the jet out from where the bowl was, and take the main jet out. Replace with the new jet and put the bowl back on. WIth the airbox mod in the post above you will get about 2-3 HP gain and all for about ****** $3.00 *******

 

if i ride with my stock air box lid my four wheeler bogs when i hit the gas

 

any1 try the outerware lid cover? looks like a cheap way to remove ur airbox lid w/o buyin the k&n powerlid for $100 or having extra crap on ur air filter!

 

EHS RACING TRX 400EX PART NUMBER 400EXCS =$67 VOICE 607 847 8765.
KEEP YOUR OLD LID FOR WASHING AND SWAMPING. EHS FOR HAULING ***. DOES A GOOD JOB OF KEEPING SPLASHED WATER OUT BUT I WOULD BE CAREFUL WHEN THE EHS LID IS ON. YES I AM REJETTED AND PIPED.
ALSO K&N & OUTERWEAR.
IF YOU GET ONE GET A LIGHT COLOR SO YOU CAN SEEE THE DIRTYNESS OF IT.