Hey, i got a 2003 400ex wit e series exhaust and filter, and renthals. I want to get more power and was thinking of getting either a 416 or 426 kit. does anyone know how reliable these are and about how much money they cost? i also want to get it ported and put a 450R carb on it and some new cams. if anyone could tell me how reliable this would be and how much it would cost it will help a lot.

 

with gasket, boring, piston, cam, 450r carb and throttle cable the price should be less than $600. this is assuming you do the work, besides boring. it is a pretty reliable setup if done right.

 

Agreed!