416, 425, or 440??

[Mitch400EX]

I'm looking to bore out my cylinder in the near future. anyone have any preferences as to a 416, 425, or 440? I'm particularly interested in any info on the 416 and 425. Also what are the bore specs for each kit?? I don't drag race or anything, I just want a little more get up and go mainly for MX and hard play riding.

[400MXer]

if your just lookin' for more power, and not to race or anything, you could get out cheap by putting a standard bore, high compression piston in, with an XR400 cam. not only cheaper, but will give pretty good gains.

as for 416 or 425, i've heard(don't quote me on this) but a 425 will really reduce reliablity because you are boring your stock sleeve so thin.

i heard the curtis sparks 416 is faster than the competitions 440 i have a piston in my 400 and i can easily beat my friend on his 440 and i have much crisper throttle response

[Poncho]

A 416 revs faster than a 440 and I don't know much about 425's;)

if you want a 440 get the ducan 440emx kit
an if you want a 416 get a curtis sparks kit with xr400 cam. :p
Personaly I like the 406 myself

just my 02.:D

ther must be sumthin wrng wit ur buddys 440, u shouldnt be able to beat him wit jus a piston, even a real high comp

[Matt Fisher]

Flyinex- what cam is your're friend using?

Mitch400EX, as an engine gets larger, it will make more torque. The stock cam is so small that it starves a higher compression 440cc motor, killing the top end horsepower. It'll have tremendous low-end, but won't wind out very well.

Assuming you step up to a good size cam (GT Thunder, TC Racing, etc), a 440 will make more horsepower and torque than the other motors.