No engine number ?

[WINGS]

Hi folks fairly new here (although have been a registered user for a while).
Name is STEVE and have a few XS's which brings me to my question,
I have recently picked up what I believe to be an XS 1 the Frame number is S650-001062,am I correct with the XS 1 however there is no engine number on it at all which poses a conundrum why ? any ideas thoughts would be most welcome.
I have included a few pics for reference.
Cheers
STEVE

 

[gggGary]

Motor sure has all the early XS1 indications, might be a set of replacement cases from Yamaha, any cases ordered through them would not have been stamped. From here it doesn't look like a number was removed.

 

[WINGS]

Motor sure has all the early XS1 indications, might be a set of replacement cases from Yamaha, any cases ordered through them would not have been stamped. From here it doesn't look like a number was removed.

Hi thanks for the help, the casing definitely hasn't been tampered with.
Bonus for me I can now have matching numbers
Cheers
Steve

 

[Paul Sutton]

The finish on that case seems very good compared to the one below and the base of the cylinders above. Perhaps it is a Yamaha replacement part as suggested by gggGary above.

 

[5twins]

I think they are a matching case set. You do have matching 4 digit numbers on the back side. That would seem to indicate they were machined together for the bearings (as they should be) and are a matched set.

 

[TwoManyXS1Bs]

Triple ditto.

The head shows the period correct early fin damper buttons.

The engine cases are replacements, latter-half '71 XS1B cases.
The original XS1 and early-half '71 XS1B case would have the reinforcing gussets behind the left rear cylinder stud, as shown here.


These gussets were dropped in mid-71 production...

 

[5twins]

That's an interesting tidbit 2M. What about the slotted holes on the valve covers? Was that a factory thing or some P.O. mod?

 

[xjwmx]

These gussets were dropped in mid-71 production...

There was a huge controversy on my block about whether the cylinder would bust off now.

 

[TwoManyXS1Bs]

... What about the slotted holes on the valve covers? Was that a factory thing or some P.O. mod?

I don't have any definitive date and part revisions on those very early "slotted" valve covers. GggGary has them on his early XS1.

http://www.xs650.com/threads/listening-to-what-an-old-hoss-is-trying-to-tell-me-xs1-wake-up.43086/

With that early S/N, and signs of a very early XS1, I'd recommend reviewing these service bulletins, and the early engine change chronology (near the end).

http://www.xs650.com/threads/yamaha-xs1-xs1b-xs2-tx650-tech-bulletins-service-data-brochures.31022/

There was a huge controversy on my block about whether the cylinder would bust off now.

Haha, I'm of the belief that those reinforcing gussets were to support the thin case overhang, in case of spewing a chain...

 

[gggGary]

An early engine will also have the screw on clutch adjust cap on the LH cover with the early 3 spline worm. Listen to 2many I was hoping he'd spread his knowledge here. With those replacement cases would be interesting to see if it still has needle small end bearings.

 

[xjwmx]

I'm thinking a whole replacement engine is more likely than replacement cases, for a couple of reasons. Have to assume a lot rarer than an original engine with sn, fwiw.

 

[650Skull]

Found this difference in the cases. No idea what year the upgraded case is but the non brace case is early XS1/1B.........Rear engine mount case bracing

 

[TwoManyXS1Bs]

I'm thinking a whole replacement engine is more likely than replacement cases, for a couple of reasons...

Back in the day, we didn't stock spare engines, weren't available, import restrictions. Don't know of anybody else who could get and stock new engines either.

Case replacements were usually done for accidents (usually insurance paid), for rod/crank failures, and for chain spewing. Not an everyday thing, accompanied with a complete overhaul, probably the most expensive service...