Con rod lenght

[Graham]

Is it possabile to fit a longer rod to a crank , eg. a 64.5 to a crank that has a 56.5 rod, without having to relocate to big end pin

[brent j]

Put a spacer under the barrel equal to the difference in rod length and modify the inlet and exhaust on a two stroke

Spacer and longer cam chain or push rods on a four stroke plus inlet & exhaust although sometimes the accessories will just "twist" a bit and line up.

I've done both in the past

[Nathan S]

Piston with a shorter pin to crown height.

[Freakshow]

All of the above or some of, but depends on what you are trying to do?

what are you trying to do and on what would help the answer