For Sale - 1972 Yamaha GS650 (XS650 w/factory 750cc engine)

I think what you are missing on the 750 kits is the sleeves are removed, block bored and new sleeves installed.
Notice you can get them for 256 or 447 motors. Very common mod done since they came out with the XS650.

http://www.hoosracing.com/new650750engineparts.html

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Dont accuse me of trollingso your point is to insult me?
, Dont answer with insults.
Don't worry about BluzPlayer, he has a habit of calling me a crybaby so i changed my avatar so it isn't an insult
650 sleeve cylinder wall pictured, diameter across is 75 mm. if the 750 is 80 mm diameter, subtract 2.5mm from each side.
That leaves the cylinder walls about 1mm thick on each side,
am i wrong and why?
View attachment 214555


@scobman
This thread is 10 years old,. Although i agree with Jim maybe a new thread may have been better, there has be lot of discussion and information on the GS650/750 over the years already discussed and posted in this thread, so i personally have no problem with it being in this area.

I think you have got yourself stuck in a loop and having trouble relating any new information and not letting go of what you already think........not a criticism just something that happens.

A 3mm oversize, (from 75 to 78mm bore) only increases the sidewall 1.5mm to give an overall diameter of 3mm larger...........1.5 + 1.5 = 3mm

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And as to your assumption the sleeve is getting thin when boring out to the 706cc piston, that is a yes, (but not so thin as the sleeves can't accept 78mm pistons), but only if the machinist doesn't go slow, or tries to take off to much in one cut instead of doing 2 or 3. Then the sleeves can warp if to much heat is generated by taking off to much meat in one cut

Any thing larger than 706cc the sleeves have to be removed from the Barrels. The Barrels have to be bored out to accept larger Sleeves to accommodate the 750cc, (80mm) pistons.
 
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As mentioned above, the OP is ten years old.
I wonder if the bike in question ever got sold and how close it came to that $15,000 figure ?
I can accept that to some folk the bikes special history gives it some special value.
But to me it's just an XS2 with a 743cc big bore kit fitted, and I'd base my valuation on the condition of the bike, mileage etc.
Still a very desirable machine but I wouldn't pay a premium price just because it's a factory special.
As for the the "GS650" designation, rather than the more logical "GS750", I've got my own theory about that.
I'd guess that the factory just rounded up a batch of 200 XS2's straight off the production line.
Maybe their competition department did all the conversion work and then simply stamped a "G" in front of the S650 engine and frame numbers.
In a strange parrellel, I think Triumph Corp in America built the T120RT 750cc twin using a Routt big bore kit, and simply stamped a "T" on the end of the stock T120R moniker.
Apparently (suprise), due to the high value of the T120RT, there have been a number of forgeries detected.
I wonder if anyone has got hold of a "G" stamp and tried the same trick with an XS2 ?
 
Good lord riding the 1972 xs650 at 150mph, i dunno, those skinny front wheels with the cloth embedded thread in the rubber tires at 10 and 2 oclock to prevent slippage. A normal early year 650 can get you up to about 110 maybe a bit more depending on your how much guts you have.
The 72 TX-750 has a much wider front wheel for a reason and listed at 186mph top speed. Why need better brakes somebody asked.
Why need to make a special XS-750 when the TX-750 existed and then forget to badge it an "GX"
The GX may of been the Police bikes they made but werent they white and green? "GX" meaning government ??? Ive heard of those but they dont look like a brilliant red xs2.
If that is real theyre probably worth 15,000 because it comes with a great story.
A 72 TX 750 went 186 mph pushed out of a cargo plane at 37000 feet....
 
I wonder if anyone has got hold of a "G" stamp and tried the same trick with an XS2 ?
Would be tough to do as there is a 200 number sequence for them. Along with the G the rest of the serial number would have to be correct.
 
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.

Ok Scob.
I'm going to try this one last time.
You can indeed advertise your 427 corvette as a 454 corvette if indeed the engine in it is now a 454. If that is the case it would be incorrect to advertise it as a 427 since it is no longer a 427.
You could NOT legitimately advertise it as a FACTORY 454 corvette.

As for the GS650....
The GS650 was a FACTORY by Yamaha special edition. It was created to allow yamaha to use the 750 engine in their race bike. The rules specified that a certain number of bikes had to be sold to the general public to qualify as a production bike for the classification they were competing in. They did not care about badging and it was not created for mass sales. It was a very limited number that were built and sold for the sole purpose of qualifying the motor for competition. It based on the xs650 as that was the bike they had been competing with and was the next logical step in the evolution of the racing program. They did this with the least amount of addtional costs as possible. Others here can correct my errors but that is the basics of the bike's creation as I understand it.
As for the stock front tire you are continually rambling on about... the stock front tire is more than adequate for a 100cc upgrade as long as the rubber is good.
The GS650 will look like an XS650. I may be incorrect but I don't think they even used big fins on the conversion. The numbers tell the story.
You are absolutely correct about the GS650. I know of 2 of these bikes and I personally own one myself. I was a the Yamaha Dealer when it was unloaded from the truck new. The dealer showed me the GS650 serial numbers on the frame and engine and explained the significance of this bike and why it was built. He owned it for awhile then sold it to a good friend of mine. A few years later I bought the bike. So I know the complete history of this bike.
Love your avatar.:thumbsup:
Do you have a TZ750??
Yes..... 1976 TZ750c
 
If only somebody had proof, instead of stories. Or a picture of something real.
They said Fire melted the steel on sept 11 2001, most people believed that too.
Maybe 1.5mm sleeve walls can withstand the heat of a modified 4 over 650 motor?
Its an air cooled motor, Id expect the sleeves to at least glow red as your racing the bike down the track.
 
If only somebody had proof, instead of stories. Or a picture of something real.
They said Fire melted the steel on sept 11 2001, most people believed that too.
Maybe 1.5mm sleeve walls can withstand the heat of a modified 4 over 650 motor?
Its an air cooled motor, Id expect the sleeves to at least glow red as your racing the bike down the track.
You have been told, several times in this thread, that the bike is well documented. You have also been told to call Yamaha yourself if you are so unconvinced. The proof is there, if you don’t want to do the leg work because you’ll find out you’re wrong, then that’s on you and you should no longer take part in this conversation
 
If only somebody had proof, instead of stories. Or a picture of something real.
They said Fire melted the steel on sept 11 2001, most people believed that too.
Maybe 1.5mm sleeve walls can withstand the heat of a modified 4 over 650 motor?
Its an air cooled motor, Id expect the sleeves to at least glow red as your racing the bike down the track.

4th oversize is 1mm............In today's market .5mm can be considered 1st oversize when it is in fact, 2nd oversize.

in real terns.
1st oversize .25
2nd Oversize .5
3rd oversize .75
4th oversize 1mm

Standard size, (650cc), liners can be taken out 3mm to 706cc
 
I knew there was a photo of the GS 650/750 barrels some where showing the factory ground off 653 stamped 754 some where. Not the best pic.

From this post.
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Maybe 1.5mm sleeve walls can withstand the heat of a modified 4 over 650 motor?
They didn't use stock sleeves. They used oversized sleeves and bored the block for the sleeves.
Same thing that is done today.
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