SR650 - Want bigger rear wheel

Hi. I have a SR 650 which has the 16 inch wheel at the rear. Im looking to change this out with a 18 inch wheel. What are my options regarding this? Any ups or downs regarding a bigger rear wheel than before? And does it exist any wire-wheels that would fit (both front and rear)?

my mistake wrong wheels

Ops!! Sorry about that.. The reason for that is that Im building an XT 500 Tracker, and was looking for interchangeable wheels for the front which are smaller. Don't know why I had that in mind when I wrote this thread..

Anyways.. I want a BIGGER wheel! Not a smaller

delete

70"s KZ1000 and KZ750 twins have a 20mm rear axle, the 650 has a 17mm, so that's a PITA swap for the rear. 650/750 twin/1000 (through 1980) have the same size front axle though, so that's an easy swap. Just use your front rotors and calipers, they bolt right on.

Maybe one of the other 650 models has a rear wheel you can use.