I know I can fit a 12 on my fork, but what does it take to install one on the rear? New swing arm? And I am using street rubber.

 

why would you want to do that? bigger tire=harder working motor=less power

 

bigger motor + higher gearing + larger tire = better for commuter duty. I am going to run my 10's for a while, till I get enough in the "fun money" to buy a 110cc + 4spd/manual clutch. But now that I am building my bike up, I figured that it would be easy to do it all at the same time.

and it's more difficult to find a speedometer for a 10" wheel, then a 12. Most here are for the monkey, or the ape. 8" and 12".