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I don't think a bearing race would work at all. You're asking the rollers to grip a machined bearing surface covered in oil. You guys with lathes, chuck up a piece of 12L14 or some other easy cutting steel, lubricate it with engine oil and try to cut it using HSS. I watched my nephew do that after I told him to use cutting oil, almost fell off my stool laughing, because he couldn't make the first cut, the bit just slipped around it.
And that's what will happen if you try using a machined bearing surface on that gear, the rollers will never grip.

By the way, good to see the elusive MrFluffy again! Escapee from the 750turbo board and ex-pat Brit living in France, IIRC, but a knowledgeable fellow in spite of all that

It's not hard to get access to that gear, so why not install it and after a couple months open it up and take a look to see how things are going? Any particles small enough to get through the oil pickup screen are going to get caught by the filter anyway.

My $0.10 worth, YMMV, etc.


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I like Steell's answer for obvious reasons. Mostly because it means this might not have been a complete waste of time and money.

Since I'm obviously no machinist (or engineer) help me understand what's going on with that gear. Steell you're saying, that the rollers would slip on a smooth bearing face when lubed with engine oil. Would that also be true of smooth hardened steel? Because that's effectively what that's turned into over time.

Originally it was hardened steel with some grooves cut in it. Over the years the grooves were worn down until the surface was completely smooth.

Here's a photo of a NOS starter clutch gear from a KZ650 (courtesy 650ed). How did those grooves help the rollers grip?

Case harden it yourself.

I would have done the press fit race or something similar myself. Those clutch designs are strong, not like the tip of a cutting bit.

Kidkawie wrote: Case harden it yourself.

Is that something an amateur with out welding tools can do?

Perhaps this article will answer some questions
www.hemmings.com/hsx/stories/2006/03/01/hmn_feature20.html

www.blacknitride.com/index.html

Minimum batch fee is $200

Sorry, taking my response down. I'd go to another site and ask what to do.

Les

It's just a basic sprag set up like in any auto tranny,
Looking at Topper's pic of the unit the outter part is
the ring the inner is the sun and the roller's are plantet's.

First all this turn's counter clockwise in that pic.
Look close you see the little wave spring next to the roller that
lightly load's the roller as the ring turn's it pinch's the roller against
the sun gear if the sun gear isn't harden'd it will fail.

I assume they reduced the diameter of the shaft before they pressed the repair sleeve on? If that gear is through hardened they had to grind the shaft to size.

Please get a file and see if you can make a small cut anywhere on the gear. If the file can make a small cut in it, then it's not hardened, if the file does nothing, or leaves a tiny scratch, then it's hardened.

Zukdave, you are correct in that it is a sprag clutch, and should have left out the part about "sun, ring, and planets", because it bears no resemblance at all to a planetary gearset.

A straight answer to your question.

The starter clutch boss should be hardened.
Not mild steel.
If you repair with mild steel i'd be surprised if it worked more than once or twice before failing.
To repair the existing boss it will need to be ground undersize and a hardened ring shrunk on and then that ground to the correct size.

I been here now and then steell, I just noticed the forum on tapatalk hence my current visit means I can sit in bed on a sunday on a tablet browsing.

Like you say its a simple sprag cluch, the friction isnt to bite the roller into the gear to stop it skidding (you dont want that), the roller is supposed to get just enough friction to roll up the ramp in the sprag and jam. Its the wedge action that locks it, also why the original gear is deformed, over the years its been pushed into by the roller so much its got deformed by it. It's supposed to be round and uniform like the rollers that come out squashed into funny shapes by years of use too. Thats generally why you replace the clutch, because this surface gets too deformed and beat up.
Maybe I'm being anal about how hard it needs to be, but they were factory hardened. Take a file and scratch the original gear, if the file just skips over it, that'll give you an indication it was hardened. Remember also, its only doing anything when the motor is starting, after its cranked its thrown back out of mesh and centrafugal force is enough to overcome the springs wanting to push the rollers coming back down the ramps into contact again.

Les, was it something I said? Repair sleeves are intentionally thinner than bearing inner races, this is what I was referencing but in the shaft version.
www.bartlettbearing.com/products/em-quik-sleeves/

The original gear was definitely hardened steel. The machinist mentioned it after working on it. And a file won't do anything to it.

From a little reading on case hardening, it seems like i should be able to find someone who can do that. In fact, the machine shop I used ought to be able to do it.

There seems to be enough doubt about this working as is that I'm hesitant to install it on the bike. I'm going to see if I can at least get it case hardened first.