hi i have a 2001 400ex stock my question is that i want to make a 426 out of it my buddy told me that all i need is a 80 over piston if i go 80 over on the bore that seems like it would make it a 440
does anyone know what size piston i need to make this bike a 426
and i would like to buy a packge deal with matching parts cam, piston, ect. for the 426 but i cant find any web site that sells evething in one package can anyone help
thanks

 

Umm if you go 80 over your 400ex will be a 480. The only people that i know of who make a 426 piston are J.E. and maybe wiseco. That is a ggod choice piston right there. The thing it has going for it is the fact its light, so it can rev fast, plus its a larger bore than stock so you get added hp and torque. I am pretty sure you can get a piston kit from JE for about 139.99 plus tax. If i were you i would get a stage 2 hot cam to go along with it. The stage 2 will give you alot more top end power, and on a 400ex thats where i feel it needs it most. You don't lose all that much bottem power either. It i were you i would get a good after market full system exhaust, and quality aftermarket airfilter, that way you have your motor a little more protected. If you do all that your 400ex will have some really good 300' times if properly geared for your weight. And an awesome trail bike. If i were you i would go look on ebay for parts. You can find stuff that dealers and other people sell that is still brand new, not even opened from its package. Plus you can save alot of money that way also. I think if you just add all bolt on stuff besides the 20 over bore job your motor will remain pretty reliable. Plus you have the added comfort of knowing its a honda.Lol. What kinda riding are you gonna be doing? If your going into racing i would look into a 440 kit from wiseco, which i have heard nothing but good things from. But if your into just riding fast and want more power thats the way to with what you have started to look at. Oh and don't go to crazy with your compression either, like i did on my z. I am running around 14:5.1 and all i do is play race, and fast trail ride. But i have to run 112 true blue race fuel which cost the better side of $5 a gallon. Well good luck. Peace.

 

he nailed it right on the spot, ebay and, i have bought all my goddies off ebay, i got my big bore kit cam piston, sleeve and all shipped for 280 which is a hella good price considering just a cam costs over $160 from a local dealer. the other guy said it all!

Wreckless

 

ok thanks that help out a lot but the shop here keeps saying that i need that 80 thousandth over piston to be a 426
what should i do just forget them and look on ebay for a 426 set up
i dont race just ride woods mostly and hill clim nothing xtrem lol.

 

Hey, just a little more info for you.
Do you want to go from standard bore to biggest (440)?
You can step up.
.020 over is a 416
.030 over is a 426
.040 over is a 435
.060 over is a 440

80 over (.080) WILL NOT make your 400ex a 480!
Ebay has a JE piston with stage II hotcam for a buy it now price of $269.00
The piston is for a 426cc over bore (.030 over) and does not require a resleeving of your cylinder.

 

Oh sorry i just wasn't thinking when i said it would be a 480, if bored 80 over. My bad. Wouldn't it be like a 460? I forgot the fact the 400ex is only 396cc to startwith. For some stupid reason i thought it was a 406. That would explain my bore sizes getting all messed up.

 

Just to let you guys know to make your 400ex a 426 you need to bore it out 120 over stock....
The piston size is 88mm and you use a 89mm head gasket when you put it back together...
I would go with a J.E piston

 

my bike has the 465 stroker kit in it. talk about maximum power. this thing has some amazing torque AND top end. now all i need is a cam and a decent exhaust system. just my .02

 

I have a 416 and it is .080 over,the .120 overbore is the 426.If you want to go to a 440 you have to resleeve it

 

why waste a good jug wait till you need to bore it then go up in small increments.