I apologize for bumping this old thread, but while resurrecting a GTR that hasn't run for the last thirty years I got to looking at the cylinders, looking at the jugs on the other dozen that I have parked in the shop I came to the conclusion that unless you are the original owner or know the bukes complete history from new, you really can't draw any reliable conclusions from what cylinders are on it. The bike I'm currently working on is number 1927. The left cylinder has cutouts, antiring pins and the unimproved exhaust flange. The other which shows signs of being replaced has no coutouts, no antiring pins and the improved exhaust flange. The two newest GTRs that I have are numbers 9663 and 9730 which would be very late bikes. I am unsure of the history of 9663, but it does have cutouts, improved flanges and no pins. 9730 belonged to the son of the local dealer. I know that the jugs are original to that bike. The red/chrome tank GTR that I bought new in early 1970 (wish I still had it) had cutouts, anti ring pins and I am unsure of the exhaust flanges. I do however know that when I seized a piston in 1973, that the replacement had no cutouts and no pins. I have two NOS sets of cylinders and both of them hace no cutouts, improved exhaust flanges and no pins.
When new these bikes were often entry level bikes and received a lot of abuse. Most had a cylinder or sometimes both changed over the course of their usage. One friend of mine bought a new GTO in 1971 and hated the smoke so much that he turned the pump way down. He would go through a couple of cylinders a year. Some people would use any oil that was handy. All I'm trying to say is that you cannot assume that the jugs are original to the bike w/o knowing it's history for certain and you can only come to a rough idea as to when each type of cylinder was put into use.
Sorry for being so long winded.
