How Fast would my 400ex go if I Bored my cylinder 80 over then get a 11:1 pistion and A Gt thunder cam then I am going to do some porting. The next thing Is what kind of pistion.

 

i gor an .080 JE 10:8:1 piston and that's all. I didn't feel like waiting for the cam (I will get one soon)

I didn't get much power gain. But once i got the jetting CLOSER to right it seemed a little better
i bet my top speed is like 76

 

67.26478904

 

mid to high seventies, maybe higher with high gearing, I run 16/34 for high speed road riding (85 mph is my new best speed, thats CRANKIN

 

I"ve got a friend, who has 400ex, that bored to a true 400cc, and has duncan double barrel pipe. It's also got a kand n, a stage four jet kit, wiseco piston, and i'm not sure if he has a cam. But it will run in the 80's cause he has ran along side a car goin eighty and kept up with it.