Odd marks on tach drive shaft?

[bosco659]

I have the right side case cover off to replace clutch springs and replace the steel spacer at the base of the tach drive shaft. I inspected the driveshaft and noticed an odd finish on the end of the shaft. Looks like fine grooves or serrations in the shaft. Is this normal? I was thinking maybe it’s to aid in oil distribution around the shaft end in a blind hole?

 

[Jim]

Is this normal?

Yes.
All of 'em I've pulled out have those machining marks. Not sure why.... oil retention perhaps... or just grooves from cutting the gear. Dunno.

 

[5twins]

Looks like the remnants of the spiral gear after the end was turned down. If you look at it, you can see they align perfectly with the lows in the remaining spiral gear.

 

[bosco659]

Good observation regarding the grooves lining up with the gear. Maybe they machined the gear first and then spun the bottom of the shaft to the correct OD for the pocket in the cover. Surprised that shaft in that application wouldn’t have a smooth finish since it’s riding in aluminum.

 

[Jim]

Maybe they machined the gear first and then spun the bottom of the shaft to the correct OD for the pocket in the cover.

They (design) were in charge of the hole and shaft size. That makes me believe the grooves were intentional for oiling. If you think about it, they could have just as easily made the hole smaller and machined the shaft end smaller to remove the tooling marks from making the gear. Makes me think they're intentional.

 

[gggGary]

I've always thought it was just an oopsie on the engineers part, and they figgered it would do no harm and mebby a little good...
Don't forget the spacer/washer. After several tries I finally found a good stainless replacement part with correct ID, OD, thickness.
* don't ask me what size or where found cuz I don't remember. Fark.
I make a point of installing with the sharp spacer edges facing the gear not the case.

 

[bosco659]

I've always thought it was just an oopsie on the engineers part, and they figgered it would do no harm and mebby a little good...
Don't forget the spacer/washer. After several tries I finally found a good stainless replacement part with correct ID, OD, thickness.
* don't ask me what size or where found cuz I don't remember. Fark.
I make a point of installing with the sharp spacer edges facing the gear not the case.

I bought a spacer from Yamaha. Guess I should have measured it. Maybe still can…. Stay tuned.

 

[Beags64]

12mm OD, 8mm ID, .043"/1.1mm?

 

[gggGary]

View attachment 235259View attachment 235260

12mm OD, 8mm ID, .043"/1.1mm?

You made me look for it! On an XS1 "showing low miles" I got;

 

[Wingedwheel]

That washer can easily become an issue if you don’t know it’s there. I’ve usually gotten lucky but shouldn't that washer size be put under the sticky’s in tech?

 

[gggGary]

That washer can easily become an issue if you don’t know it’s there. I’ve usually gotten lucky but shouldn't that washer size be put under the sticky’s in tech?

You've read my mind. (scary space) I'm adding that pic to the great o-rings seals etc. thread.

 

[Wingedwheel]

You've read my mind. (scary space)

We are all just brothers from another Mother….