Odd Z1 starter clutch.

On the right is a clutch we received in a parts lot. It appears new, but we believe it's been in service.

On the left is a used clutch representative of every other Z1 starter clutch we've ever seen.

The red arrow on the left clutch points to the hole in which a 6mm pin, PN # 551A0622 mates into a matching hole in the dyno rotor. The clutch on the right lacks this pin hole.

As an aside, on many of the starter clutch / dyno rotor assemblies we've disassembled the pin has sheared, and the three bolts holding the clutch to the rotor chewed up from relative rotation. Seems two or even three pins evenly spaced, and maybe larger in dia., around the circumference for balance, would have been a better design choice.

There are a few service bulletins related to mods of the overall starter gear / damper / needle bearing / starter clutch & rotor assemblies that live on the crank, but we've found nothing about the pin or lack thereof between the dyno rotor & starter clutch.

One-off fluke from Mama Kaw? Early Z1 clutch simply sans pin hole that was never documented?

Good Ridin'
slmjim & Z1BEBE

Hi Jim/Z1BEBE - the pin appears to disappear around 1980 with the switch to the later style generator (ref CMNSL slides) so it may be a later part that you have

Wookie58 wrote:

Hi Jim/Z1BEBE - the pin appears to disappear around 1980 with the switch to the later style generator (ref CMNSL slides) so it may be a later part that you have.

Yes! It's from a later machine ( MK2 onwards ) with the dished rotor. 

I'm using a pin from a 630 chain. The rotors have three holes for 1 pin. It would have been better if they used all three. I don't see why they didn't unless they were made to fail. 

I'm going to try to  drill and match two more pins to a old rotor to see if it can be done. 
BTW the 630 pin is holding up after two years. 
Steve

The problem with those clutches is that the rotor bolts are fully threaded and a very slack fit in the holes.
This allows the rotor to shift around on accel and decel which eventually loosens the bolts and allows them and the pin to shear.

The cure is to sleeve the holes in the clutch to snuggly fit a plain shanked bolt .


And then fit some modified (shortened) bolts (on the left)  with a plain shank that fits the sleeved holes with no play.


Once done there is no movement and the pin isn't needed.

zed1015 wrote:

The problem with those clutches is that the rotor bolts are fully threaded and a very slack fit in the holes.
This allows the rotor to shift around on accel and decel which eventually loosens the bolts and allows them and the pin to shear.

The cure is to sleeve the holes in the clutch to snuggly fit a plain shanked bolt .

And then fit some modified (shortened) bolts (on the left)  with a plain shank that fits the sleeved holes with no play.

Once done there is no movement and the pin isn't needed.
 

Outstanding mod!  Thanks for posting.

Could you please elaborate on the sleeves?  Off the shelf tubing, or machined ID / OD  to fit?

Good Ridin'
slmjim & Z1BEBE

Thanks for the responses everyone!  Our Z1 tunnel vision makes this kind of mistake inevitable.

Good Ridin'
slmjim & Z1BEBE