Spline-style wrench ID

Pulled out the bendix on my old Madura today, it had seized up. A little bit of wrenching freed it up, but I still don't know why or if it's going to seize again. It's a non-servicable part, but that has never stopped me.

I also have a "new" on the way from Ebay just in case, but curiosity is getting the better of me. Problem is the 29 tooth "spline head":

It's 29 teeth, OD is appr 23.5mm ID 21.8 (or less, hard to measure). It looks like the teeth are rounded, but the chamfer makes it a bit hard to say for sure.

Is this based on anything remotely standard or completely proprietary? I don't mind making the tool, I just would like to get it right on the first try and it's impossible to measure properly.

Edited By Fulmen on 29/05/2023 22:15:30

Edited By Fulmen on 29/05/2023 22:26:27

Aw crud. I thought it was screwed together with a custom wrench, but it's just figured out it's a spline joint locked with a recessed snap ring. I'll have to compress two large belleville springs in order to get it apart. I'm sure that will be fun...

...a little *brute force* later...

It is a thing of beauty. It is also worn out.

The inner shaft has a handful of very noticeable flat spots, maybe 0.01mm deep? I gave up on photographing them, but the worst was perhaps 1mm wide. The surface finish is bright and uniform, but it has a very slight "faceted" look to it even where it feels flat. The rollers look and feel fine.

It might be possible to regrind it, but I don't have the equipment. Hopefully the replacement will be good, but you never know with second hand parts.

The "new" bendix clutch works, so old Maggie is back on the road yet again. But I always try to figure out why a part failed in the first place. In this case it might be as simple as 40years of wear, but there is another possibility.

Originally the starter was wired through the clutch handle, requiring the clutch to be engaged for starting. This was annoying as heck, in part due to the crappy switch they used so I quickly removed that. But that does result in the occasional "jump start" when I've left the bike in gear. It hasn't bothered me much really but it does put more strain on the starter...

A set of very slightly larger diameter rollers might resurect the clutch, but getting some of about 0.05 to 0.015mm plus might be difficult.

I've been pondering that myself, but I'm not sure if it's the diameter (IIRC 0,01-0,02mm below a whole number for both the shaft and rollers) or the flat spots that cause it to seize up. I didn't take the new clutch apart to check the dimensions, figuring I was doomed to break something.

I think I can make new rollers, haven't measured the hardness but I'm sure I can find a suitable material. But I'm not so sure about regrinding the shaft. Best I can muster is a diy dremel toolpost grinder.

So the first order of business should be to reduce wear on the new one. Restoring the starter lockout seems like a sensible approach. I never liked the original solution (requiring the clutch to be engaged), but the bike has a lamp indicating neutral. Adding a relay to that might be a more elegant solution.