50 cc to 70 cc

Hey guys, I'm relatively new to the st70 scene as I only bought mine a few days ago.
Stupidly when I bought the bike I just assumed it was a 70cc engine and missed the huge 49cc mark on the cylinder, my own fault .
i was wondering if I I would be able to upgrade the barrel and piston to 70cc and still be able to use the head, or would I have to upgrade the lot?

Thanks for any answers

Jord

Hi there is a 47mm piston for sale on ebay at the minute designed to work with a 50 head, I think a 70 piston is 47mm and a 50 piston is 39mm and the head is the same size to suit.

Thanks, i bought it, bargain