I have a 2009 evo 125cc in mint condition and due to the poor part ex deals offered against a 200cc upgrade i wondered if anybody has converted a 125cc to a 200cc .If so is at more than changing piston and head or can 125 head be bored to 200,do the jets need changing and the million dollar question COST !!!

I can't give a definitive answer but at a guess the 200 barrel would bolt straight on.

What other mods would be required could be minimal or riddiculously complicated.

It may be worth finding out what makes the 200 bigger than the 125. Is it piston height or barrel width?

You may be able to get 200cc or near it by using a shorter piston. There would still be other work required though to get it right.

Do you need a 200?

The Beta 200 is a small bore 250, not a big bore 125 so you would have to swap the crank also.

In that case you need a new bike if you need 200+ cc