is it possible to put a wider tire on the back of the 250? if so what would it take?

 

No rims not set up for it. look down a few topics there are several on tires. I will say my metzler lazertec 130/90 is a lot wider than the stock dunlop and fits on the rim fine, its also a very good tire.

Dont worry about how a tire looks so much as whether or not it will stick on the road.