I have a completely stock 07 400ex. What is the best big bore kit? i don't want like a 1000 plus dollar kit or anything. just the big bore kit by itself. I want either a 416, 426, or 440. i just want to know what are the differences so i can pick the one that i think i would like the best. and what compressions you think i can go with. anything above 100 octane is a problem. 100 is fine though. thanks for the help.

 

from what i hear the 426 is the most reliable. as far as the price of just the bbk it should be around 200-300$$ max. im not for sure but i think that you dont have to bore the cylinder out like on the 440. but i hope you have a good exhaust and a more free flowing air filter and a jet kit. if not your not going to notice a hole lot of power gain. if you have enough cash get a new cam, and maybe a carb off a 450r, that would open it up nicely!!