TOPIC:

I decided to have my "local" machine shop (and use quotes because it's over an hour away) do some machine work on a spare starter clutch gear for my '79 KZ750. This part is specific to the '76-'79 750s, was discontinued long ago and is impossible to find NOS.

They put a sleeve on the worn down boss and applied a texture to match the surface seen in some photos of NOS gears from similar year 650s (Thanks to 650ed).

My concern is that they used mild steel and had no way to harden it. They said the gear itself was hardened steel. There are some steel rollers that ride along the edge of the boss. Is this going to work or will the mild steel sleeve get worn down in no time?

Here are some photos.

"Mild steel" really doesn't tell me anything, that term can cover a huge range of steels.

I think I would have case hardened it before putting it on the gear though, since all you need is surface hardness.

It will still probably last a long time though.

That gear fits the following models:\

KZ750-B1 (1976)
KZ750-B2 (1977)
KZ750-B3 (1978)
KZ750-B4 (1979)
KZ750-G1 (LTD II) (1980)
KZ750-K1 (LTD Belt) (1983)
KZ750-K2 (CANADA ONLY) (1984)
KZ750-M1 (CSR Twin) (1982)

I knew it did but I had to check the parts diagrams to make sure. I have an 82 750 twin motor in my 79, and I bought the motor with no stator/flywheel/etc, and installed 78-79 parts on it.

Sorry, Better answers to be had elsewhere

Les

Define "fail miserably". Would this be potentially dangerous? Or it just won't last long?

Go to a good bearing supplier and buy a repair sleeve the right od to match the original.
Take sleeve to your ship and ask them to fit it on your part with a light interference fit loctite etc.
Thousands of bearing fits are restored in industry like this daily.

Topper wrote: Define "fail miserably". Would this be potentially dangerous? Or it just won't last long?

the surface will chew up and put flakes of metal into the oil, so it isnt very healthy for things.
I think les and I are referencing almost the same item, but I know them as repair sleeves, and i think they are thinner wall than inner races so need to remove less parent metal, important if you are repairing a stressed part.

MrFluffy wrote: Go to a good bearing supplier and buy a repair sleeve the right od to match the original.
Take sleeve to your ship and ask them to fit it on your part with a light interference fit loctite etc.
Thousands of bearing fits are restored in industry like this daily.

Damn. It sounds like this was a big waste and I'm going to have to start over with a new part.

One more question for you. The guy at the machine shop said if I wanted it hardened, I could send it off to someone with an oven who could harden it for me. What's he talking about? Who would I send it to and would that work?

in the interest of clarity are we talking about the flat (horizontal in this pic) surface,outlined in red?



leon

Not exactly, no. The boss on the gear was sleeved. In this picture, the part between the red lines is the sleeve.



The rollers for the starter clutch ride along the face of that sleeve. You can see how it works here:

it would seem that you wouldn't want it to have a hardened surface or the rollers wouldn't be able to "bite"into it enough to hold it.

leon

Hmmm... The whole gear was hardened steel originally. It also had a texture to it which the machinist replicated. I'd assumed that texture was to help the rollers grip somehow. Or maybe to give the engine oil an escape path so the rollers wouldn't slip so much. IDK.

Obviously I don't want a bunch of metal shavings in my engine oil. But the original parts seemed to have lasted 30+ years and in the case of my bike 25,000+ miles before they wore down enough to fail.

I'm not looking for this one to last another 30 years. I just don't want it to shred in 1000 miles either and spit all that steel into my oil.