Can you put smaller wheels on a Honda xr 100?

Not sure on other years, but the XR80 and XR100 1985/86/87 used the same frame. The XR100 had the same diameter forks, but 50mm longer than the 80, and the swingarm was 50mm longer also, but the wheels were interchangable, IE: the XR80 wheels would bolt straight onto the XR100. The XR80 had 14 inch rear and 16 inch front wheels, the XR100 had 16 inch rear and 18 inch front. HTH