CNW e start conversion, sprag failures

dobba99

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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.
 
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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...
 
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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.
 
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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…
 
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.
 

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