Hey guys, im going to be getting a new 400EX, because mine was stolen on july 29th. Anyhow, I left it all stock but this time I wanna go with some modifications.

I was thinkin of a white brothers pipe. what about jetting and what about air filter/box modifications? Going to be riding very aggressive trails, hillclimbs, and gravel roads.

I really dont do the porting and boring out crap, or even the high compression stuff, I dont care for that. Anything else is game.

Please help out
thanks

 

It depends on what you like, but the UNI foam filter is a good filter and not very restrictive. Alot, of people also run K&N, but once you put an outerwears on it, they are supposed to flow the same as foam.

If you don't ride in deep water you could try an outerwears airbox cover. The one I had required cutting like a 3x3 square out of the lid and then you put the outerwear over top of it, but I think there is one that replaces the lid entirely.

Another, option would be a high rev box. It will allow you to start your attack on a hill at higher rpm, and then as your motor dies down going up the hill you will get back into the 400s sweet spot. With an exhaust, air filter, airbox mods, and rev box you will probably be jetted around 152-155 main and 42 slow jet. Keep in mind this is using original keihin jets, I have now clue about the dial-a-jet kits.

There are several chassis mods that would help too. One would be some decent handlebars like tags or renthals. An aftermarket steering stem with anti-vibe mount will help you out too. I like the Holeshot XCT 22" tires for the back too. Helps out with the 400s miserable ground clearance on trails. One other thing might be an aftermarket swingarm. The stock aluminum one will hold up well on trails, but tends to break pretty quickly when jumping. Alot, of people go to a plus one which might help on hillclimbs if only a little.

 

Check out the Graydon pipe. Its pretty good.