what kind of big bore kit should i get for my 400ex and how can i cool it better and what new things would i need to put on my 400ex if i bought a big bore kit for my ex.

P.S if you know can u tell me how much extra horsepower it will give my ex
Thanks

 

i'd call powroll or sparks

 

i wouldnt go above 440, i think powroll has a good one

 

A 440 will give you some extra hp.

 

what kind of riding do you do?