Don't know about the front tire but a 245 wide auto tire is the largest rubber that'll fit in the rear. The 245/50ZR16 Goodyear Eagle F1 is probably the widest to fit as it only gives a sliver of clearance to the drive shaft swingarm. It measures about 260mm wide at the widest points so far as mototires go, you might be able to fit something close to a 260 wide.
Good luck finding wider moto-tires to fit the stock rims though. The selection is nil at the moment. Gonna have to get different rims if you want more selection.