Boring out your cylinder gives very very little power increase. you wont even notice it.
You can buy a 240cc cylinder but a ported stock cylinder will wipe the floor with 240's all day.
Just stick around and read stuff for a while before you start throwin out all kinds of questions. lol everything you need to know about a blaster is here
Just like Scot said read around youll find helpful answers. It is not a great idea to bore cylinder like that besides youll will have barely noticable power gainage. I say ride the Bores all out... Or go with a 240.
It's been done. Somewhere in the archives I have pics of such a swap.
I guess the only drawback to a swap like that is the cost and time.
It would be cheaper to just buy a shee.