upgrade my 05 400ex

[buster024]

Where/how should I start if I want to re-bore my 400? I'd like to go to a 426. I've currently got a full Yosh exhaust + K&N, UM scoops, and outerwear. Is there a multiple step process that I can do a little at a time and not be out of a quad and lots of dough all at once? What's my first step?

[Wandell]

Well, you've already done the first mods eveyone suggest. If you still want more power, you might as well go to a big bore kit. Or you could just sell it and get a 450.

[400exrider09]

Originally posted by Wandell
Well, you've already done the first mods eveyone suggest. If you still want more power, you might as well go to a big bore kit. Or you could just sell it and get a 450. sounds like u have already done a lot of mods to it if ur still looking for speed id get the big bore kit (440) if ur not interested in selling it.

[miller821]

Originally posted by buster024
Where/how should I start if I want to re-bore my 400? I'd like to go to a 426. I've currently got a full Yosh exhaust + K&N, UM scoops, and outerwear. Is there a multiple step process that I can do a little at a time and not be out of a quad and lots of dough all at once? What's my first step?
If you want to make it a 426, I would first bore it out and put in the piston, then you can buy cam, and more.

[buster024]

so, i need to by a large bore kit...?? Is everything i need in one kit? Any recommendations for brands/types?

[NCexRider]

You shouldn't even need to bore your cylinder on a motor that new. Get a stock bore high compression JE piston, a Hotcam, and port and polish and you'll be happy. Maybe a heavy duty cam chain also.

[TacomaNC4X4]

or dont get a 450 and still have reverse and better handlng. not to mention, less stuff to go wrong on a 400.

[PowerJunkie]

Originally posted by TacomaNC4X4
or dont get a 450 and still have reverse and better handlng. not to mention, less stuff to go wrong on a 400.

:huh :huh what is there to go wrong on a 450? and if you bore it i would be more worried then owning a stock bore 450.

[buster024]

Sooo......since i'm still not a motorhead (trying to learn), if my decision is to not re-bore, but rather to use a stock size high compression piston, do I still need to dissasemble my bike and have them port and polish, or can that be done with the motor still in the frame. After that is done, if I had the time & patience (and a live connection to exriders forum), is it reasonable to assume i could install the hotcam & piston?

[buster024]

Also, what's the difference between a stage 1,2,3 hot cam? If i'm predominantly a dunes rider (80% sand, 20% trail), which should i lean towards?

[NCexRider]

The hotcam stage 1 gives more low end power, stage 2 gives more mid/top range power. I'd go with the stage 1 personally. I'd find someone who knows what they're doing in your area, pull your motor, take it to them and have them install the high comp piston, hotcam, and do the port and polish. There's no reason to port & polish if you're not installing the other parts.

[B-rad D]

What compression ratio ?

[buster024]

if you're asking me about the compression ratio i'm at a loss. What should I be after?

[NCexRider]

10.5:1 (stock bore) or 11:1 to still run pump gas.

[krt400ex]

Originally posted by buster024
Where/how should I start if I want to re-bore my 400? I'd like to go to a 426. I've currently got a full Yosh exhaust + K&N, UM scoops, and outerwear. Is there a multiple step process that I can do a little at a time and not be out of a quad and lots of dough all at once? What's my first step?

You can start by buying a cam, but that's about it because if you get a piston then you've wasted $100 on an a piston because you will be upgrading to a bigbore piston soon.:)