Yamaha History Buffs - Need Help - 1972 XS750 200 made?

ilbikes · Post by **ilbikes** » Fri Jan 30, 2009 10:30 am

Fellas, I have a very good friend who has just purchased an awesome 1972 Red/White XS650 with 1,100 original miles. The bike is just fantastic. Paint, seat, rims/spokes - untouched, unmolested. He called me last night and asked me to help him trace down one little issue.

The owner says this bike is one of 200 1972 XS650s to have a factory installed "750 kit". The story goes that Yamaha gave full factory warranty and put these out there to test the durability and acceptance. The cylinder is even stamped "750cc".

What gives? Anyone ever heard of this?

Thanks,
Gordon

Wayne Meuir · Post by **Wayne Meuir** » Fri Jan 30, 2009 1:48 pm

Gordon, Yamaha made a 750 twin around that time and it was a compeletly different bike. Not sure what they called it. A friend had one back when they were almost new and is was a total pile of cack. They had a horrible rep.

Wayne

Arne · Post by **Arne** » Fri Jan 30, 2009 3:32 pm

Wayne Meuir wrote:Gordon, Yamaha made a 750 twin around that time and it was a compeletly different bike. Not sure what they called it. A friend had one back when they were almost new and is was a total pile of cack. They had a horrible rep.

Wayne

In 1973 and 1974 Yama made all the XS series bikes TX series.

The XS650 was just named a TX650, but the TX750 was it's own bike with a counterbalancer to make up for the large rotating mass.

The 1973 bikes all blew up if you revved them at idle as the rotating mass frothed the oil and the pump wouldn't pump it.

The 1974 TX750 was a really good bike, but the damage was done and Yamaha went back to XS650's in 1975. The 1973's got warrantee engines in them.

This is what they looked like:

GT Tim · Post by **GT Tim** » Fri Jan 30, 2009 3:57 pm

Here you go Gordon...

Wayne Meuir · Post by **Wayne Meuir** » Fri Jan 30, 2009 4:13 pm

Yup, that's what my buddy had, and it WAS a piece of crap!

Wayne

ilbikes · Post by **ilbikes** » Fri Jan 30, 2009 5:14 pm

Guys, this fellow knows Yamahas - his 1971 Gold/White XS650 has won 1st place at the Barbers VJMC show every year. He has 2 1971's, a 1973 TX650, a 1978 triple 750, an several other models including old two strokes and a brand new FJR.

Here is the all-original XS650 - that is original paint, the fender doesn't even have rust underneath. The engine cases are 1972 cases - not an engine swap. If Yamaha didn't do it, then we're thinking maybe a dealer with access to Shell dirt track parts back then. This bike has not been touched or ridden in 30 years. Look at the inside of the chaingaurd on this red 1972 1,100 mile bike! The only thing we can find on his not stock is the mirror, rack, and crashbar. The handlebar, switches, seat - everything else looks stock. Anyone putting a 750 kit in for performance would have changed the carbs, pipes, and air filters - these are 100% stock.

Oh yes, I am familiar with that t u rd of a TX750 twin in 1973/74. This is different.

The last 2 show both his and my 1973 TX650's.

Gordon

Wayne Meuir · Post by **Wayne Meuir** » Fri Jan 30, 2009 6:09 pm

The engines on the bikes in those pics are definately NOT TX 750 engines. The TX 750 looks totally different.

Wayne

Arne · Post by **Arne** » Sat Jan 31, 2009 9:34 am

Interesting. I've never heard of a 750cc XS650, but who knows.

Are the rest of the cylinders differnt? Could it be someone bored it out and changed the 650 to a 750? I imagine 100 cc's could be had by boring.

Interesting, and in any case he's got some very nice bikes. I've always wanted a XS650 from 72 or a black one from 75 or 76... those are nice looking bikes.

Most of them go to ice racers around here though.... oh well.

Arne

GT Tim · Post by **GT Tim** » Sat Jan 31, 2009 8:32 pm

http://thehive.modbee.com/?q=node/11489

cyclebuster · Post by **cyclebuster** » Mon Feb 16, 2009 12:53 am

TX 750
Toyota eXperimental.
1972 cooperative engine project, this was an air cooled version of a twin cam V6 Toyota racing engine. Very succesful engine, everywhere but in the Yamaha. Have had several TX750, and never saw one run. Parted every single locked up dead one of them. TX500 just as bad a joke.
Guy i knew had a TX500 with a horrendous knock in it. Thing ran forever. last summer a guy shows up at the shop with a TX500 rat bike. Same knock.
This is the 2nd time i have heard the XS750 twin story. Its more then likely a MORGO top end kit. they were stamped 750cc

tz375 · Post by **tz375** » Sat Mar 14, 2009 9:21 am

Gordon,

Obviously it's not a TX750 top end, but did you find the real answer to the mystery?

I don't recall Morgo doing anything other than a T120 block though there were people in the UK with big blocks, but I suspect that was much later.