piston size

[xX-400racer-Xx]

i was wondering if an 87mm piston was a 440 with stock head. this is what i thought but a website i found the other day said that it was a 416.

[FoxProRacing]

a piston that have a 87mm bore is a 416

87/2 = 43.5

3.1416*43.5*43.5 = 5944.6926

5944.6926 * 70mm (stroke) = 416128.482

416128.482 / 1000 = 416.128cc

[FoxRacing81]

87mm is 416
88mm is 426
89mm is 440

[FoxMxRiders]

Originally posted by MX610EX
87mm is 416
88mm is 426
89mm is 440

89mm is not a real 440 ... just a 435

:rolleyes:

[TC426EX]

Originally posted by FoxMxRiders
89mm is not a real 440 ... just a 435

:rolleyes:

Thats why you gotta specify for an 89.5mm piston for a true 440