This bike is for real as I also have one. I bought mine from the original Yamaha dealer. I was there at the dealership when it was delivered new from Yamaha. The frame and engine have matching FACTORY stamped letters and serial numbers and have been verified with the Yamaha dealer and Yamaha Corp. in Buena Park Calif. The serial numbers on the frame and engine begin with GS650 instead of S650 and the only other obvious difference is the cylinders have "743" stamped in. The reason for this is Yamaha did not cast new cylinders for only 200 bikes. They just installed 750 big-bore sleeves in stock castings, removed the cast-in "653" and hand stamped "743" on them. The rest of the motorcycle is exactly as any other 1972 XS-2 650 motorcycle. The serial number sequence is GS650-102651 thru GS650-102850. Although there are probably thousands of 650s with 750 big-bore kits installed, if the frame and engine numbers begin with S instead of GS it is not one of the 200 issued by Yamaha. I hope this clears up any confusion about these unique bikes. If you have any questions please e-mail me at TZ750@att.net.
All 200 GS650s came with 750cc cylinders installed. If your bike was a true GS650 but had 650cc cylinders then someone removed the 750cc cylinders and replaced them with 650cc cylinders. I still have mine and I know of one other guy that owns one. Check your frame and engine numbers. If it is stamped S650 then it is a standard XS650 that came with 650cc cylinders. If it is stamped GS650 then it is 1 of 200 XS650s that was delivered to dealers with 750cc big bore cylinders.
Pictures of the stamped 743cc cylinder would clear it up, due you have a picture of that?
What does the title say, maybe a picture of that too.
A lack of pictures, pictures of the frame neck sticker and a picture of the 743cc stamped cylinders would end the debate.
if the title says s650 xxxxxxxx vin but the bike is stamped GS650 xxxxxxx wouldnt the DMV give you some grief?
the outside diameter of a 650 sleeve about 79-80 mm without measuring
if the tx750 rings for std size pistons are at 80mm
LOLA lack of pictures, pictures of the frame neck sticker and a picture of the 743cc stamped cylinders would end the debate.