1936 model 19

Hi Richard,

   82mm + 80 thou is virtually 84mm and as there are no Norton pistons this size, you may have to consider using a piston from another make of machine. You could try a Vincent Comet or Rapide as these have a similar crown height to a Norton and a 7/8 inch gudgeon pin as per Norton. Another option could be an AJS/Matchless which is 82.5mm as standard, so a plus +60 will take it up to 84mm and this also has a 7/8 inch pin. 
   If your piston it out of the engine and you are able to get to auto-jumbles, you could compare either of the above or perhaps another make. There are 3 things to check, the crown height, the pin size and the weight. Don't go over 84mm as this will make the lower section of the barrel too fragile.