CNW e start conversion, sprag failures

My bike #101 was built 2013 and I bought in 2024 with just over 10k miles. It now has 22k. However the bike only had the E start kit fitted in 2021 and I’ve no idea what the mileage was at that point.

However I reckon it likely the owner put most of the miles on in the early days and then reduced to the point of moving it on.

Matt may well know and I’ll ask next time I contact him but my guestimate would be 8k.

I always kick the bike over from home and only use the E at petrol stations and pubs/cafés etc or anytime I need to start it whilst astride it so not a heavy user but if the wear is mileage dependent then roughly 12k ish

CNW starter installed spring of 2019 at 5,500 miles.
First sprague failure 6,300 miles later @ 11,800 miles CNW replacement installed.
Second sprague failure 6,700 miles later @ 18,500 miles (Chinese) sprague installed.
Two bearings in the kilt failed 4,100 miles later @ 22,600 miles. Heat related I believe. The grease in the bearings was black and crystallized and bearings partially seized. Installed new bearings and changed sprague with another new (Chinese) sprague because it was already disassembled. The first Chinese sprague was still working properly.
4,000 miles later @ 26,000 miles everything is fine. First two spragues installed lubricated as received. Chinese spragues had atf for lube.
My bike probably has very few starts compared to some as I ride it between 100 and 200 miles every time I take it out, usually only stopping for fuel.

Sounds like every 6k mi for your riding. You have 2k mi to go.

Hutchison hemi said:

CNW starter installed spring of 2019 at 5,500 miles.
First sprague failure 6,300 miles later @ 11,800 miles CNW replacement installed.
Second sprague failure 6,700 miles later @ 18,500 miles (Chinese) sprague installed.
Two bearings in the kilt failed 4,100 miles later @ 22,600 miles. Heat related I believe. The grease in the bearings was black and crystallized and bearings partially seized. Installed new bearings and changed sprague with another new (Chinese) sprague because it was already disassembled. The first Chinese sprague was still working properly.
4,000 miles later @ 26,000 miles everything is fine. First two spragues installed lubricated as received. Chinese spragues had atf for lube.
My bike probably has very few starts compared to some as I ride it between 100 and 200 miles every time I take it out, usually only stopping for fuel.

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Thanks for the information, Question, which bearings failed?

dobba99 said:

Thanks for the information, Question, which bearings failed?

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The bearings that failed were about 2 inches in diameter and about 1/4 inches wide from memory. There is also a very small diameter bearing which was ok.

Hutchison hemi said:

The bearings that failed were about 2 inches in diameter and about 1/4 inches wide from memory. There is also a very small diameter bearing which was ok.

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Ok, the two bearings either side of the sprag. Apart from replacing the sprag as a service item another thing to do, when your in there replacing the sprag, is to remove one of the rubber shields from these two bearings, clean out the old grease, repack with a high temperature grease and replace the rubber shield.

So, I recently installed my cNw starter kit this spring at 8929 on the odometer. I'll see how many miles I get out of it before any of this happens to me. Seems like I should expect it too around 15k on my odometer. I use the start each time I ride, and generally ride on the weekends for about 100 miles. So, it will take me a while to get to 15k. My kit would have the latest bearings that Matt uses which I believe is different than what was used before 2020 when most of you guys seem to have had your kit installed. We'll see how it goes. I have the Shorai LFM21 w/315 cold cranking amps so lots of juice to spin the starter well enough.

Bummer that this is a complication of electric start mechanics, but knowing that this is an issue and serviceable easily enough, makes me think to get spare parts on hand for when it happens and do a refresh of the kit bearings each 5k miles or so. Probably overkill but what isn't on our bikes....

Starvingphotog said:

So, I recently installed my cNw starter kit this spring at 8929 on the odometer. I'll see how many miles I get out of it before any of this happens to me. Seems like I should expect it too around 15k on my odometer. I use the start each time I ride, and generally ride on the weekends for about 100 miles. So, it will take me a while to get to 15k. My kit would have the latest bearings that Matt uses which I believe is different than what was used before 2020 when most of you guys seem to have had your kit installed. We'll see how it goes. I have the Shorai LFM21 w/315 cold cranking amps so lots of juice to spin the starter well enough.

Bummer that this is a complication of electric start mechanics, but knowing that this is an issue and serviceable easily enough, makes me think to get spare parts on hand for when it happens and do a refresh of the kit bearings each 5k miles or so. Probably overkill but what isn't on our bikes....

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I see all this talk abought the CNW E start I have an earley kit the only problems that I had where a sprag lock up after a kickback after 2 failures from a kickback Matt sugested that I replace my Pason ing with a sparks ing no more kickback and no sprag lockup [ lock up means all dogbones jamed and not able to engage ] the other problem that I have and have not seen any one talk about is failure of the adjustable detents they ware out and will not stop the gears from spinning cause a iritating wine noise Matt sent me several updated sets with hardened ends they siill wore out and stoped working I find it hard to beleve that I am the only one to have that problem I have modified the start motor [ relocated the spring ] so that the gear stays ingaged and removed the detents the gears now stop as soon as te bike starts sorry the italics falt of my computer

I have an Alton and I think the the CNW is a beautiful piece of kit. I think CNW do a great job. From this thread, I think that CNW sprag dog bones being in contact while engine is running does makes for a sometimes shorter life sprag for some of the sprags. However . . .

My perspective it that I am really grateful that many parts manufacturers and vendors invest so much that us Commando owners can buy all parts needed to keep our 50 plus year old bikes on the road. I just rebuilt my 850 engine (first time I have done an air-cooled) and thanks to all your help, I have 800 miles on it and I am happy knowing all is done right.

In the big picture, Commando parts prices are very reasonable. Have you looked at the today's parts cost for a 10 to 15 year old car?
Many cars reach an age where they are worth less than the single repair needed.

I don't expect perfection from all the parts I buy. Yes, in my engine rebuild some gaskets did not fit, some inlet valve guide seals had rough lips, one superblend bearing ran stiff after shrinking the crankcase around it, and the new tach seal must have come from the wrong parts box.
I was not upset with my supplier. I am grateful I can get parts.

So, like others, I now regard the CNW sprag as a possible maintenance item. One can lube it every couple of years and/or replace it after x thousand miles.

There are some manufacturers out there who care. But were they to design every part as perfect, this thread would say some parts are too expensive and the part would not sell.

These are my thoughts and I hope that if Matt sees this thread, he knows that I think his products are great and that if one of his products has a suggested maintenance of lubing or replacing a sprag, that would not deter me from buying his products.

Dennis

ebyker said:

I see all this talk abought the CNW E start I have an earley kit the only problems that I had where a sprag lock up after a kickback after 2 failures from a kickback Matt sugested that I replace my Pason ing with a sparks ing no more kickback and no sprag lockup [ lock up means all dogbones jamed and not able to engage ] the other problem that I have and have not seen any one talk about is failure of the adjustable detents they ware out and will not stop the gears from spinning cause a iritating wine noise Matt sent me several updated sets with hardened ends they siill wore out and stoped working I find it hard to beleve that I am the only one to have that problem I have modified the start motor [ relocated the spring ] so that the gear stays ingaged and removed the detents the gears now stop as soon as te bike starts sorry the italics falt of my computer

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Interesting, I wonder when you had the sprag locked up and the engine was driving the starter gear train this might have caused the holes where the adjustable detents engage to get a track worn into and out of them. This would make the detents less effective at stopping the gear train after the engine has started.

dobba99 said:

Ok, the two bearings either side of the sprag. Apart from replacing the sprag as a service item another thing to do, when your in there replacing the sprag, is to remove one of the rubber shields from these two bearings, clean out the old grease, repack with a high temperature grease and replace the rubber shield.

Click to expand...

That is what I did with the new bearings.

DennisMo said:

I have an Alton and I think the the CNW is a beautiful piece of kit. I think CNW do a great job. From this thread, I think that CNW sprag dog bones being in contact while engine is running does makes for a sometimes shorter life sprag for some of the sprags. However . . .

My perspective it that I am really grateful that many parts manufacturers and vendors invest so much that us Commando owners can buy all parts needed to keep our 50 plus year old bikes on the road. I just rebuilt my 850 engine (first time I have done an air-cooled) and thanks to all your help, I have 800 miles on it and I am happy knowing all is done right.

In the big picture, Commando parts prices are very reasonable. Have you looked at the today's parts cost for a 10 to 15 year old car?
Many cars reach an age where they are worth less than the single repair needed.

I don't expect perfection from all the parts I buy. Yes, in my engine rebuild some gaskets did not fit, some inlet valve guide seals had rough lips, one superblend bearing ran stiff after shrinking the crankcase around it, and the new tach seal must have come from the wrong parts box.
I was not upset with my supplier. I am grateful I can get parts.

So, like others, I now regard the CNW sprag as a possible maintenance item. One can lube it every couple of years and/or replace it after x thousand miles.

There are some manufacturers out there who care. But were they to design every part as perfect, this thread would say some parts are too expensive and the part would not sell.

These are my thoughts and I hope that if Matt sees this thread, he knows that I think his products are great and that if one of his products has a suggested maintenance of lubing or replacing a sprag, that would not deter me from buying his products.

Dennis

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Afternoon Dennis
I agree with almost all of what you say. I also am very grateful that we have one of the best spares supply to keep our commandos on the road.
That said, if Alton supplied their kit so the drive is taken through the engine sprocket instead of the alternator key, that would improve its reliability and more importantly not damage the crank. This can be done with the Yves mod outlined on the forum a while ago. Another failure point of the Alton is the flyleads from the alternator. these are solid wire, not flexible and are very prone to vibration and consequently break, I personally have repaired a couple of alton stators with this fault, fitting them with flexible leads. This is an example where the manufacturer can improve his kit by listening/learning from customers.
Alton did learn the hard way that they had used the wrong epoxy to glue the magnets into the rotor, they had a habit of flying out when the glue let go.
I do think that aftermarket kit suppliers have a tendency to use the customer as a long term product evaluation, they might not intend to, but, if they had to wait for every fault to manifest itself it would/could take years.
Cnw have been supplying these kits for at least 7yrs and i find it hard to believe that i was the first to realise there was a design fault, and i don't even have one!, i saw some photos that showed how the sprag was being used. CNW should be on the ball with a remedy, not just sticking plasters. Maybe they possible view the repeat sale of new sprags as a guaranteed income stream.

Hutchison hemi said:

That is what I did with the new bearings.

Click to expand...

Good

dobba99 said:

Afternoon Dennis
I agree with almost all of what you say. I also am very grateful that we have one of the best spares supply to keep our commandos on the road.
That said, if Alton supplied their kit so the drive is taken through the engine sprocket instead of the alternator key, that would improve its reliability and more importantly not damage the crank. This can be done with the Yves mod outlined on the forum a while ago. Another failure point of the Alton is the flyleads from the alternator. these are solid wire, not flexible and are very prone to vibration and consequently break, I personally have repaired a couple of alton stators with this fault, fitting them with flexible leads. This is an example where the manufacturer can improve his kit by listening/learning from customers.
Alton did learn the hard way that they had used the wrong epoxy to glue the magnets into the rotor, they had a habit of flying out when the glue let go.
I do think that aftermarket kit suppliers have a tendency to use the customer as a long term product evaluation, they might not intend to, but, if they had to wait for every fault to manifest itself it would/could take years.
Cnw have been supplying these kits for at least 7yrs and i find it hard to believe that i was the first to realise there was a design fault, and i don't even have one!, i saw some photos that showed how the sprag was being used. CNW should be on the ball with a remedy, not just sticking plasters. Maybe they possible view the repeat sale of new sprags as a guaranteed income stream.

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Thanks. I did have a broken alternator lead and now I solder the alternator wires to the leads that pass through the case. How did you add flexible wires and where

DennisMo said:

Thanks. I did have a broken alternator lead and now I solder the alternator wires to the leads that pass through the case. How did you add flexible wires and where

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The wire had broken just as it emerged from underneath the coil so I had to rewind the coil to get to the end. then solder them to flexible leads.

Nice.

Someone asked up thread about symptoms of a failing sprag. This is the sound my bike made the day after I came home from Italy last week; I was shocked and thought the worst; something, a bearing perhaps was on its way out. As it happens the E Start was miraculously working perfectly which through me as I didn’t then consider the sprag to be the culprit. Most obvious when it stops and then starts again, yikes!

Today I dismantled the primary side (again) and removed the sprag and transfer gears/bearings and took Arnie for a 35 mile ride. Perfect. That racket was the sprag. Not saying they would all do that but this one did; standard 14 dog as fitted by Matt in 2021

Café au Lait said:

Someone asked up thread about symptoms of a failing sprag. This is the sound my bike made the day after I came home from Italy last week; I was shocked and thought the worst; something, a bearing perhaps was on its way out. As it happens the E Start was miraculously working perfectly which through me as I didn’t then consider the sprag to be the culprit. Most obvious when it stops and then starts again, yikes!

Today I dismantled the primary side (again) and removed the sprag and transfer gears/bearings and took Arnie for a 35 mile ride. Perfect. That racket was the sprag. Not saying they would all do that but this one did; standard 14 dog as fitted by Matt in 2021

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Interesting, around 52 seconds in you can just see the transfer gear rotate slightly as the heel dragging sprag exerts its influence. Check the bearings either side of the sprag, flick one (or both) of the rubber shields out and check that the grease hasn't got dried out, heel dragging equals heat generated.

Café au Lait said:

Someone asked up thread about symptoms of a failing sprag. This is the sound my bike made the day after I came home from Italy last week; I was shocked and thought the worst; something, a bearing perhaps was on its way out. As it happens the E Start was miraculously working perfectly which through me as I didn’t then consider the sprag to be the culprit. Most obvious when it stops and then starts again, yikes!

Today I dismantled the primary side (again) and removed the sprag and transfer gears/bearings and took Arnie for a 35 mile ride. Perfect. That racket was the sprag. Not saying they would all do that but this one did; standard 14 dog as fitted by Matt in 2021

Click to expand...

The replacement sprag that Matt sent me has 18 dogs. Not sure if that would make any difference.

I have an Alton. Its' dog bones are not in constant rotational contact compared to the CNW design.
However, I have learned a lot in this thread and the CNW sprag is simply a maintenance item.
I would buy it. They make great kit.
Dennis

I found the following on-line. It seems that some (or maybe all) sprags are designed for constant rotational contact

These are results for should sprag clutch dog bones always be in contact with rotating parts or be retracted by centrifugal force
Show original results

Sprag clutch "dog bones" (or sprags) are typically designed to maintain constant contact with the inner and outer races. They are held in place by springs to ensure instantaneous engagement when the direction of rotation changes, though some specific high-speed clutches use centrifugal force to pull them away.

Sprag clutches operate based on your specific application and type:

1. Constant Contact Sprag Clutches (Most Common)

• How They Work: Sprags are individually energized by ribbon or garter springs so that their curved lobes are always touching both the inner and outer rotating races.
  
• Why it matters: Constant contact ensures there is zero "lost motion" or lag. When the races attempt to rotate in the opposite direction, the sprags immediately bind and transmit torque.
  
• Risks: If constant contact isn't maintained, some sprags might catch before others during a direction change, resulting in uneven torque distribution and potential permanent damage to the ⁠sprag clutch springs.
  

2. Centrifugal "Lift-Off" Clutches

• How They Work: Certain specialized, high-speed ⁠overrunning clutches use a centrifugal throwout design. When spinning at a very high overrunning speed, the centrifugal force of the sprag's mass overcomes the spring pressure.
• The Result: The sprags physically lift off the race, eliminating all rubbing contact, which significantly extends the wear life of the internal components.
  
• Limitations: These clutches have a minimum "lift-off speed." The drive mechanism must ensure the speed stays below this threshold during the torque-transmitting phase to allow the sprags to properly re-engage.