Got a problem trying to fit a wet rear tyre & wheel to my 1988 nc23,the wheel is wider & the cush drive & sprocket are much larger than the one in my bike,i think the wet tyre/wheel is from a 1990 bike but not sure.Anyone got any ideas why the wheels are so different.

Is it a 3 spoke or 6 spoke wheel you are fitting?

It has 6 spokes & is 17 inch diameter,it is also wider than the rear wheel which is fitted in the bike.