turning a 90cc into a 50cc

[fasttimes]

Ok got a question!
I have a 90cc motor with a 42mm crank and a 52mm bore, Can I get a different jug to make it 50cc or 70cc legal?

:confused:

[jandjracing]

I think for it to be "legal", you are not allowed to downsize the engine to meet class cc requirements.