CNW e start conversion, sprag failures

[dobba99]

After my post about modifying the roller cam sprags to fit the Mk3 i was asked if they would fit the CNW e start conversion kit (as apparently they use the same size of sprag i was told) Upon looking at the CNW design it is obvious that the installation of the sprag in the e start kit is not how the sprag is designed to be fitted. These sprags are designed to run clear of the inner race when in operation (engine running)
In the Mk3 commando, the centrifugal force throws the dogbones away from the drive gear snout.
In the CNW drive gear/engine system, the sprag is stationary (it fits in the drive gear) so there is no centrifugal force to throw the dogbones clear, and when the engine is running the dog bones are constantly dragging their heels on the engine pulley snout. So a sprag failure is baked in from the start.
My question to all CNW e start kit users, how many have suffered sprag failure?
My answer to the chap who asked me about the sprag fitting into a CNW e start kit, was to treat the sprag as a service item, replace it at regular service intervals, and hope CNW come up with an upgrade to correct this mistake.

 

[MexicoMike]

Although I don't have the CNW E-start (I have an Alton - the CNW E-start didn't exist back then), I have bought a considerable number of CNW components and this would be the first time I have ever heard that CNW produced a product with a faulty design that needed correction.

It will be interesting to see the response to the question re the number of CNW sprag failures. My gut/experience reaction based on my CNW experience would be "none." But I'm prepared to be surprised...

 

[dobba99]

Although I don't have the CNW E-start (I have an Alton - the CNW E-start didn't exist back then), I have bought a considerable number of CNW components and this would be the first time I have ever heard that CNW produced a product with a faulty design that needed correction.

It will be interesting to see the response to the question re the number of CNW sprag failures. My gut/experience reaction based on my CNW experience would be "none." But I'm prepared to be surprised...

I know of at least two CNW e start owners that have had their sprag fail. The chap who asked me about them said that no one will admit that they have had a problem with their e start kit...No one wants to talk about it!
Regarding the Alton design, That has its problems as well, like the rotor key shearing and the alternator fly leads breaking. But these problems can be and have been overcome. Yves mod to the engine sprocket/drive gear sorts the rotor key problem and flexible wires cures the alternator leads.

 

[Fast Eddie]

After my post about modifying the roller cam sprags to fit the Mk3 i was asked if they would fit the CNW e start conversion kit (as apparently they use the same size of sprag i was told) Upon looking at the CNW design it is obvious that the installation of the sprag in the e start kit is not how the sprag is designed to be fitted. These sprags are designed to run clear of the inner race when in operation (engine running)
In the Mk3 commando, the centrifugal force throws the dogbones away from the drive gear snout.
In the CNW drive gear/engine system, the sprag is stationary (it fits in the drive gear) so there is no centrifugal force to throw the dogbones clear, and when the engine is running the dog bones are constantly dragging their heels on the engine pulley snout. So a sprag failure is baked in from the start.
My question to all CNW e start kit users, how many have suffered sprag failure?
My answer to the chap who asked me about the sprag fitting into a CNW e start kit, was to treat the sprag as a service item, replace it at regular service intervals, and hope CNW come up with an upgrade to correct this mistake.

Fitted mine in 2019. I use it all the time, kinda need to as I don’t have a kick start fitted!

920cc with 11:1 CR, so it’s not like it gets an easy ride…

 

[Café au Lait]

Mine fitted 2021 or about 9k miles ago, no issues and I’ve recently inspected it twice as documented in another thread

 

[grandpaul]

The one that needs fixing seems to be the Alton, although they've since changed (I believe) the number of perishable plastic "slugs" so the load on each one is lower. But they had "teething pains" with alternator, chain, etc.

 

[Jerry Doe]

I put one of the first cNw ones that was made in mine about 3000 miles ago and never had an issue. It works well every start.

 

[DennisMo]

I have had my Alton about 3 years and the sprague has been fine. I did ask Paul at Alton about lubricating it and he said that if the cover is off, inject some dry lube in to it. When I do pull it all apart, I pack some grease in it. Any thoughts?

 

[Deets55]

I have had my Alton about 3 years and the sprague has been fine. I did ask Paul at Alton about lubricating it and he said that if the cover is off, inject some dry lube in to it. When I do pull it all apart, I pack some grease in it. Any thoughts?

Since a sprag depends on friction I would be cautious about any grease on those dog bones, assuming the Alton sprag is similar to the stock E-start. I lubed my stock sprag once and had to take it apart to clean all the lube off, all it did was slip.

 

[DennisMo]

I did buy a spare sprague for the Alton from our Canadian dealer because I read about sprague failures. It has come packed with grease. My guess is about 1/4 the volume. Now wouldn't the force that locks the sprague be more of a wedge action rather than friction?
Dennis

 

[johnm]

I know of two sprag failures in CNW starters. Mine plus a friends. Mine was bought about 8 years ago now and failed within a few months. Matt sent a replacement immediately and it has been fine ever since. The second was on a bike in the UK bought as a transport backup for the IOM Velo team. I don't think that's been replaced yet. I don't know what era that starter was bought in.

It's an easy fix and it seems the sprag bearings Matt uses now behave themselves.

I have been meaning to buy a spare for years now. Should get on with it.

 

[robs ss]

I have nearly 18,000 miles on my cNw since early 2020 and no problems to date (touch wood!!)
I have recently bought a tube of lub specifically for dry-running sprag bearings - haven't put it on yet, as the thought of pulling it apart doesn't fill me with joy somehow. Go figure... ?
BTW, where did the sprague spelling variant come from?
Cheers

 

[ashman]

I have nearly 18,000 miles on my cNw since early 2020 and no problems to date (touch wood!!)
I have recently bought a tube of lub specifically for dry-running sprag bearings - haven't put it on yet, as the thought of pulling it apart doesn't fill me with joy somehow. Go figure... ?
BTW, where did the sprague spelling variant come from?
Cheers
View attachment 125071

But Rob you keep telling us you still use your kick start all the time and` occasionally only use your starter to see if it's working, or have you gone to using the ES now all the time, so no troubles with it in 18K mile trouble free, but how often do you use the starter, but 18k on the ES whether you use it all the time is not much mileage at all, but different if you not using it all the time it should have even less troubles, well no troubles at all.
Sorry Rob thought I throw that one at you and what are mates for hey lol.

Ashley

 

[robs ss]

But Rob you keep telling us you still use your kick start all the time and` occasionally only use your starter to see if it's working, or have you gone to using the ES now all the time, so no troubles with it in 18K mile trouble free, but how often do you use the starter, but 18k on the ES whether you use it all the time is not much mileage at all, but different if you not using it all the time it should have even less troubles, well no troubles at all.
Sorry Rob thought I throw that one at you and what are mates for hey lol.

Ashley

No Ash, you're right, I nearly always kickstart but what the OP was saying is the sprag dogbones are dragging all the time, regardless of if you use the estart or not.
Mine is (cross fingers) still okay anyway

 

[MexicoMike]

I bought the Alton shortly after it became available/installed it in late 2012. Had problems with the original alternator rotor disintegrating (twice). Both times Alton immediately sent replacements - literally overnight - the second time with a revised rotor. I installed that rotor in early 2013 and the system has been bulletproof since then. I removed the bike's kickstart lever 5-6 months later and it's been only E-start since then.

FWIW - a bit about the original rotors: Both of mine failed not long after installation. Second one blew on a ride about 40 miles from home outbound. I turned around and the bike made it home with no trouble on the Shorai battery/TriSpark. Both rotors literally grenaded, blowing out magnetic shards all throughout the chaincase. I sent pics and some remains back to Alton. In discussions, Paul advised that they thoroughly tested the rotors at RPM much higher than the Commando achieved so initially they didn't understand the failures because rotors/adhesives used in the construction easily withstood 10,000+ RPM on a test machine.

Then, he explained, they were discussing the problem and someone in the shop (maybe Paul, I can't remember) decided to play some heat from a propane torch on a spinning rotor. The rotor promptly disintegrated! Turned out the rotor supplier/manufacturer hadn't factored engine heat into the selection of the epoxy used in rotor construction! The rotor was then modified to use different adhesive AND add a metal "cap" over the circumference of the rotor. As I said, been bulletproof since...

I have no experience with the CNW E-start though quality-wise, based on all my experience with CNW, I have always assumed it was more robust than the Alton. However, even if the CNW E-start had been available at the time I probably would have still selected the Alton because it allows the retention of the OEM Ham Can air filter assembly which was very important to me. It is also less "visible."

 

[Bonzo]

I have had my Alton about 3 years and the sprague has been fine. I did ask Paul at Alton about lubricating it and he said that if the cover is off, inject some dry lube in to it. When I do pull it all apart, I pack some grease in it. Any thoughts?

I emailed Alton to enquire about this when I had mine apart for the 'Yves modification'....

Good morning Laurent.

Thanks for confirming the number of inserts. I have now inserted 6 of the new items and am ready to re-assemble.

Can I ask another quick question?

The sprag clutch appears to have a dark coloured grease/lube coating the inside. Can I ask what this is, so that I can apply a little more?

And Laurent replied...

I think the color of the grease after some use is not really significant.

We are using classing bearing for our initial workshop assembly (EP2).

 

[robs ss]

GMN Bearings, who manufacture sprag bearings, recommend the following lubricants (I bought to first one). @ashman , you may consider these for your assembly, unless something else is specified in your instructions?

Post in thread 'Sprage Clutch'

Dec 2, 2025

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

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

• robs ss

 

[kokomoto]

I recently had a sprag failure. Matt had a replacement in stock and sent it to me.

 

[YING]

Dobb,
Just curious if you have talked to Matt about your concerns.
Mike

 

[dobba99]

Dobb,
Just curious if you have talked to Matt about your concerns.
Mike

Yes