Pros and Cons 440 or 425 Big Bore Kit

[staysblazed]

I need to get a big bor kit for my 2001 400ex. I dont want to have to keep working in the quad all the time. I want reliability with limited maintanence. Which is the way to go?? The 425 big bore with the 11:1 piston Or the 440 kit with the same piston. I want to run only pump gas not race fuel. I want the engine to last a long time.

[JPhonda]

personally if it was me building the motor i would put a 416 kit in it. they are the most reliable bore to go with and they also proform good from what i hear. They rev up faster then the bigger bore motors. out of the two that you talked about i would go with the 426 because its going to run cooler and you still have room to bore it out more incase it ever needs it.