I have on their way a stage 2 hotcam, jet kit, hmf pipe. already tossed the airbox lid, and put on a k an n. Soooo. whats next, and mods that work well to build power that you guys want to throw this way?

 

Oh an I also bought a sprocket kit

 

whats next is to get rid of that k&n filter they let too much dirt through!!!

 

K&N will work as long as you have a good pre-filter, you keep it clean, and you don't ride it the midwest dustbowl.

As far as more mods your might as well stop there. If your not happy after you install these mods you will always want more so might as well start saving for a new quad instead of putting money into it.

 

I agree with dropping the K and N. To risky in my book, I like a good old fashioned foam filter for everything with the possible exception of sand.

 

I have a prefilter and filtered airbox lid. I am happy with the power. I just want to get the most out of it. I mean I know its not gonna be anything like my 450r with the 490 kit stage 3 cam, cp head, ect. Just wondering if there are any power adders I might have overlooked.

 

Build a good 426, 11:1cr, head work, header if you don't already have one, replace the K&N with a UNI and put a EHS lid on. It won't be as fast as your 490, but it'll keep up with if not beat a 450.

 

Thats what I wanted to hear...now I have a build plan. Thanks. Do I need to machine the case for a 426, is 11:1 pump gas. (the 490 is 110 an my trail bike needs to be pump) What piston, weisco? and who does good head work. CP did the 450r head an I feel They didnt give it everything they could.

 

Wiseco pistons are good. I've had the same 440 big bore kit in mine for 6 years now and its still holding up strong! What you need (what every 400ex needs) is a BIGGER CARB!!!! FCR 41mm you'll notice a difference

 

11.1 should be fine on 91-93 octane, the 426s are fast! buddy of mine raced one before he upgraded to a trx450 that john natalie used to use, and he did good vs all the new 450s, his 426 would actually pass most 450s on takeoff, FMF powerbomb header would be a plus, better valves and springs from Webb or Kibblewhite or something, bigger carb, Dynatek CDI, porting...