Hole in First Gear Wheel ?

[Determined]

Hey all. First post.
1st gear wheel in my 1979 XS Special had a worn out bushing. Found NOS one on eBay with same part #. AFAICT all the dimensions and teeth profile are the same. Only difference is the extra hole in the gear. Can't see it causing a problem. Curious as to it's function though.
Also wondering if it is common for the bushing to fail? Besides being loose from the gearwheel it was 3.5mm narrower than the gear. Oddly everything seemed solid enough before disassembly to install tall 5th gear set. Then the bushing fell out and had crazy slop on reassembly.

 

[Determined]

And .406mm(.016") end play. Is that acceptable?

 

[Jan_P]

Well welcome
Not sure if I can say something useful
I would check online parts-number lists so the replacement gear is a substitution dimension wise.
It Actually is for your bike and year. And take into consideration that the gearbox can have been replaced.
There is almost no chance they have the same part no being so different
It is to much work to find it out later

The play is probably OK without knowing how the design looks it appears to be between the
Gear wheel and the locking circlip ( not sure the English word )
There has to be some play for thermal expansion somewhere in the design

I would be more nervous about the gear wheel dimensions

 

[Determined]

I actually found a thread where the four page factory shimming bulletin shows how to shim the loose gears. 3 out of 5 of mine need another 1mm of shimming. Everything else looks good to my eye. As soon as I get those shims I can assemble it in the case and see how it looks. Still curious about the hole in the first gear.

 

[jpdevol]

I haven't a clue about the hole. I do remember issues with the transmissions on the earlier models. Sure would like a copy of that bulletin if ya can post it or a link to it

 

[Determined]

https://www.xs650.com/threads/overdrive-5th-gear-dropping-slipping-out-to-neutral.41539/page-4

Half way down the page. A post by TwoManyXS1Bs

 

[Jan_P]

I say it again there would be no Major Company in Europe with the same part No on an item ( the gearwheel )
With a hole and another without a hole. As far as I know and even less chance a Japanese company had it then.

That would not happen --> Found NOS one on eBay with same part #

There can be revisions over the years but the part no is changed or gets an extra code at the end

Like fex
6666666- -05 -02 becomes 6666666-05 -03
or an entirely different No
6666666 --gets replace with 6666667

On line there are those revisions list newer design replaces an older ..which is fully normal in development and improvement even within the same year model. But there is till the part no difference you don't ( Generally ) have 2 different looking parts with the same No.

There is a risk that the one with a hole is for some other Motorcycle. ( or which one you bought )

Apologize if you have done it already .But if it is the wrong part. It can go terribly wrong Wrong play wrong pitch
If you provide part no on the replacement wheel
and bike specs we can look on line
I don't think I would install it before being certain it is a replacement. A lot of work and can be a safety issue.

 

[Max Midnight]

I don't know if Yamaha cast their own components or use outside suppliers.
If several supply the same part this may be how they identify the source?