MK3 Primary

Hello Mk3 owners,

I am now getting into the mysterious world of the MK3 primary. I have looked at the parts that came with the bike and I think I have to replace them, but am not sure- maybe I can fix them and save some $ (unlikely knowing how this rebuild is going).

Anyway this is the Starter Drive Gear. Can I machine it down flat or do I need to replace- see where it is worn:
These things are expensive $275


Then I have this which the sprag runs in (I am going to buy a new sprag)- I expect I have to buy a sprocket too (06-4681). I do want to use the starter motor.


What would you do? I think I am going to have to replace all this,

Cheers

That Sprague clutch must have been grinding away at it's home. Looks like it ran without oil . So much money involved. You know there are better / improved/cheaper clutches but how about machining out that buggered grab surface and fitting a bigger tougher sprague ? Anyone thought about that one ? Hunh?

Yes- I need to replace I think as its shagged out. Where is cheapest/best place to get the 2 items and a sprag?

I have found that usually Clubman is the cheapest and Old Britts is the fastest.
Bill G

I think I would try to build up that gear with weld and machine back down to the required dimension.
Jaydee

jaydee75 said:

I think I would try to build up that gear with weld and machine back down to the required dimension.
Jaydee

Click to expand...

If you were going to do this, would it make sense to make the ID slightly smaller to prevent the sprag from rolling over?

What is the minimum OD recommendation for the sprag?

I would be concerned about distortion from welding. Also is the inside of the hub hardened? Since it is a wear surface, I suspect it has had some treatment, so who knows where you will be at with weld.
Probably best to bite the bullet and fit new parts, especially if you are sending it out for welding/machining at shop rates, often around $100 per hour.
Even though my shop rate is zero at the moment, I would probably just buy the new part.
The thing about sprag failure is that it can make the bike inoperable. I had this happen when a new sprag broke its cage and the resulting debris locked everything up. Had to call for assistance and do quite a bit of roadside work in the rain to get things cleared out. Gasket tore so I just slapped it together good enough to get home (luckily only ten miles) then took it all apart again.
Because the bike starts easily and I see the sprag as a worry item, I have left it out and may remove the starter one day soon.

Glen

I have decided I need to save up and buy all new. Cannot take any chances here. In my mind the primary is the weakest point in a MK3 so I have to make it as strong as possible.

How is the other side of the starter gear where the inner part of the sprag rides? I have a starter gear I'd part with for postage if you think you need it.

The other side is in good shape. PM'ng you - I will pay for it if its good