Engine size?

[bruteman]

I recently traded for a 400ex that has a aftermarket sleeve and supposedly the biggest piston you can get for it, is there any way to guess the displacement without actually taking the engine apart. Any "guess" would be greatly appreciated, just curious it has a stage two hotcam and it runs really strong-thanks

[REDRIDDER]

MOST COMMON I WOULD SAY IS THE 440 KIT.

[Brauap]

Yea, most likely a 440, but the biggest is, what, a 505? But I doubt its the biggest.

[blue_ex_rider]

Sparks has a pistion alone that makes it a 465 without a stroked crank. But my guess is that its a 440 that is the most commonly biggest pistion used.