Sprage Clutch

L.A.B. said:

If the sprag 'flips' then it won't grip at all.

If it actually breaks as mine did with an almighty crunch, it locked the motor drive to the crank! I managed to free it by putting the bike in gear and then sharply pushing it backwards several times until the sprag eventually freed off and I could then kickstart bike.

Unaware of the level of destruction I rode home.

Stripping the primary, this was what I found...

This 14 sprag unit was the old 'split-cage' type. Thankfully the sprags are no longer made with the slots cut into the cage.

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I know it's an old post but it reminded me of my experience years ago.
Mine locked up on me but released when I kicked started and revved a bit.........the first time. It happened again a few days later and it didn't release. I revved it to the point of blowing up the armature of the original Prestolite motor. Fortunately it led me down the path of finding a Dyno Dave starter, big battery, 3 phase alternator, and new 18 sprag and associated parts. It's been 100% reliable for years. The big alternator took a while to finally sort and I'm pretty confident the Shindengen regulator has finally resolved. Three phase open as described here: https://www.shindengen.com/products/electro/motorcycle/reg/

robs ss said:

Okay.... sprags in dry primary cases...
I found a US company that makes sprag clutches (GMN Bearings) who have on their website:
View attachment 122727

I bought a 45 gram tube of the top one from an online BMX shop in Australia.

Strangely, I contacted Shell, who replied that they don't have a product for that application but I could try their Gudus S3 wheel bearing grease - It has EP additives, so off the list.
Cheers

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Hey Rob,
Appreciated the advice.
What, finally, could I trouble you to comment on regarding the suggestion for the related intermediate/ starter gears etc. in the dry primary. I was told CRC moto non fling chain lube (not wax) carefully painted on the gear teeth would work ?
Michael.

MBrewst said:

Hey Rob,
Appreciated the advice.
What, finally, could I trouble you to comment on regarding the suggestion for the related intermediate/ starter gears etc. in the dry primary. I was told CRC moto non fling chain lube (not wax) carefully painted on the gear teeth would work ?
Michael.

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Michael
I'm not familiar with a dry MkIII primary, but my cNw starter gear train, including idler, have remained unlubricated in a dry primary for the six plus years I have had it. No ill effects that I can determine.
They only turn when the starter button is pressed.
I think the argument could be put that a "sticky" lub plus clutch dust would result in a grinding paste.
I intend checking the bearings (sealed) for the idler shaft while servicing the sprag.
Cheers

robs ss said:

Michael
I'm not familiar with a dry MkIII primary, but my cNw starter gear train, including idler, have remained unlubricated in a dry primary for the six plus years I have had it. No ill effects that I can determine.
They only turn when the starter button is pressed.
I think the argument could be put that a "sticky" lub plus clutch dust would result in a grinding paste.
I intend checking the bearings (sealed) for the idler shaft while servicing the sprag.
Cheers

Click to expand...

Comparing the CNW estart to the Mk3 primary. The CNW kit bits are supported by sealed roller bearings on the revolving shafts, so no lube required for them. Gears wise for the little time the button is pressed realistically they won't wear even if they haven't got any lube. CNW Sprag problems have been covered on this forum lately.
The Mk3 primary was designed for oil lube to the chain, gear shafts, needle roller, sprag etc. Run it dry (with a belt) and you run the risk of the sprag locking up and jamming. If your lucky it just wrecks the starter system, unlucky and it could bring you off.
The Mk3's i have come across that have had belt drives fitted had the electric starter system removed.