Big Bore Kit For 400ex

i was considering putting a big bore kit in my ex once the engine starts to get a little tired. I was just wondering how much it costs and how much time is involved in it. I am also wondering which one is the best one and how much difference does it make when you do it. Does the quad feel a lot more powerful? can it hang withe the cannondale 440's

[yellowrider]

i think it could but i havent had any real seat time on a can but i have had seat time on a 440 and i smoked him

(your asking how that is possible) well the dumb *** just bore it and had a pipe in a filter thats it... so if you are going to bore it make sure you get a good cam and a higher compresson piston or its not even worth all the trouble..



i am trying to deciede to get the 416 or the 406 i heard they are almost the same but like i said i never rode these to i just like to know when i do blow em up i have more room to bore...

i am also thinking about getting some shocks thta would be the best thing to do if you really think about it.. and its only 300.00 without rezzis if you get tripple rates and you still have a reliable motor

[racin 400]

TRY a 426 my friend has one and almost every thing you got and it is very quick.Try the 426.

[carlj75]

Does the reliability of the motor go down when you bore it out? I was thinking about a big bore kit. There are so many different sizes-Why? It seems like the 440 kit would be the best but a lot of people have the 416. Which one is truly the best. I want to be able to smoke slightly modded raptors at the dunes. Any recommandations?

[oynot400]

How much do you want to spend? Money does wonderful things to these quads, that is if you got enough of it. There are several combinations to go with. I have all the goodies listed below and I am happy with it and have had no problems.
If money is no object I would send it to someone like TC or Sparks and have them work there magic. I saw a 416 (built by TC Racing) at the Little Sahara that made mine look like a stocker. It is amazing that good supension will make it faster too.
As far as my motor work, carb and exhaust I have about $1200-1500 invested. :eek: I know that you can always invest more.

[punker69q]

If you have enough money, go with the 440 bore and stroke with a heavy duty connecting rod :) combination from powroll. It's basically a stroked 416 kit, so you wont loss that much reliability and they claim that their full engine job will produce about 85% more hp (48-50 hp) :D

i'd go with a stock bore high compression piston and a agressive cam.

[DiceMan400]

It all depends on what type of riding you do..... If you want to have a good MX bike then go with the 416 or 426....... If you want a killer dune bike and want to hurt a raptors feelings go with the 440..... I am going to retire my 440 head and am doing a 416 being that I am into the MX part of our sport..... I have all the other work done like porting, polished, carb, cam, and valve spings....... You need these other things if you want your bike to run good after a big bore job......