I am rebuilding an RM80B and I thought eBay had just made it trivial to get good old IRC tyres to suit.
MINI-CROSS MOTOCROSS 3.60-14 REAR  TIRE 
MINI-CROSS MOTOCROSS 2.50-16 FRONT TIRE
alas, they will not ship to Australia. No explanation.
Anybody know of an OZ tyre place that might stock 30-yr-old  2.50-16 knobbies?  

Luke