I don't have the cylinders here, but they cylinders Tim is donating I believe are Austins old stock cylinders. If that the case 66.00 pistons had pretty low compression with really small domes. I would recommend a 66.25 or 66.50mm pistons. Ebay has a pretty good deal on them at 185.99 and 10 for shipping.
If people want to contribute that don't have parts, maybe a few people can donate cash towards the pistons. If that is the case please let me, Tim, or JB know.
http://cgi.ebay.com/ebaymotors/Yamaha-Bans...A1%7C240%3A1318