CNW e start conversion, sprag failures

This is what the tech at Cross+Morse said in email to Alan, our NOCNZ VP after he queried getting a different part number sprag which the NZ distribution rep said was an upgraded part, and his questions to them:

Alan: I have just purchased 3 of your Sprag clutches item SFB41-135 Part No 76SFB41-135 from RR Fisher, Auckland , NZ.

I had ordered clutch part No 1310145 and was told that the one I received was a model upgrade.

I am using them in the same way that RGM Norton us your Sprags to start a motorcycle.

Power from the starter motor is transferred to the outside of the sprag via a transfer gear.

This turns the crankshaft until the motor fires and then lifting off the crankshaft when the starter motor stops turning, with the outside of the sprag remaining stationary by way of sprung detents stopping the transfer gear..

Is this sprag correct for this application, I have read your notes on engaging and disengaging sprags and I’m not sure if I have the correct sprag.

Can you confirm?

Cross+Morse: For this application the sprag type is less of an issue. The sprags are designed to rotate with the outer race, and the differing sprag types (engaging/dis-engaging) only come into effect at relatively high speed with differing balance from centrifugal force.

For the application you describe, the sprag will be engaged for short periods at low to moderate speeds and will then be stationary whilst the engine is running.

Alan: I am about to fit the sprag to my electric start and have noticed that it has no lubrication. The primary case where it is located is a dry area and is driven by a belt not a chain. The sprag and transfer gear only rotate when I am starting the motorcycle.

Do I need to lubricate the sprag on assembly ? if so what type of lube and how much do you recommend?

Cross+Morse: In [this] case the sprag will require lubrication as the crankshaft will be rotating continuously.

Ideally the sprag will be lubricated by oil (Type A automatic transmission fluid), if not you can use grease, we recommend Kluber Polylub WH2. For either option it is imperative to ensure the lubricant is not an E.P. (extreme pressure) type, or contain any additives such as molybdenum disulphide, graphite and P.T.F.E.

dobba99 said:

See my answer in post #88
Both systems use the same size sprag
I have one of the ringspann sprags, lent to me as an example (came in a Cross and Morse box) and my impression is that it is too delicate for use in the Mk3 system, given that the engine vibrates i wouldn't install this type of sprag in a Mk3.

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This is the one Alan installed, and it has been running the last 2.5 yrs.

gortnipper said:

This is the one Alan installed, and it has been running the last 2.5 yrs.

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I,m interested. Is Alans bike a Mk3 or is it an earlier one using the CNW conversion kit? How many starts has Alan clocked up since it was fitted?

gortnipper said:

This is what the tech at Cross+Morse said in email to Alan, our NOCNZ VP after he queried getting a different part number sprag which the NZ distribution rep said was an upgraded part, and his questions to them:

Alan: I have just purchased 3 of your Sprag clutches item SFB41-135 Part No 76SFB41-135 from RR Fisher, Auckland , NZ.

I had ordered clutch part No 1310145 and was told that the one I received was a model upgrade.

I am using them in the same way that RGM Norton us your Sprags to start a motorcycle.

Power from the starter motor is transferred to the outside of the sprag via a transfer gear.

This turns the crankshaft until the motor fires and then lifting off the crankshaft when the starter motor stops turning, with the outside of the sprag remaining stationary by way of sprung detents stopping the transfer gear..

Is this sprag correct for this application, I have read your notes on engaging and disengaging sprags and I’m not sure if I have the correct sprag.

Can you confirm?

Cross+Morse: For this application the sprag type is less of an issue. The sprags are designed to rotate with the outer race, and the differing sprag types (engaging/dis-engaging) only come into effect at relatively high speed with differing balance from centrifugal force.

For the application you describe, the sprag will be engaged for short periods at low to moderate speeds and will then be stationary whilst the engine is running.

Alan: I am about to fit the sprag to my electric start and have noticed that it has no lubrication. The primary case where it is located is a dry area and is driven by a belt not a chain. The sprag and transfer gear only rotate when I am starting the motorcycle.

Do I need to lubricate the sprag on assembly ? if so what type of lube and how much do you recommend?

Cross+Morse: In [this] case the sprag will require lubrication as the crankshaft will be rotating continuously.

Ideally the sprag will be lubricated by oil (Type A automatic transmission fluid), if not you can use grease, we recommend Kluber https://www.crossmorse.com/images/specifications/Sprag_Elements.pdf WH2. For either option it is imperative to ensure the lubricant is not an E.P. (extreme pressure) type, or contain any additives such as molybdenum disulphide, graphite and P.T.F.E.

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I would not take anything this 'tech' has said, as being a Cross and Morse recommendation.
Take a look at this, copied from the Cross and morse website https://www.crossmorse.com/images/specifications/Sprag_Elements.pdf
The import stuff is on the twelfth line onwards:- 'The sprag element is designed to rotate with the outer housing, this being essential for correct operation of the unit'

How many hours would it take to re and re a dead sprag in a CNW e-start installation, start to finish?

dobba99 said:

I,m interested. Is Alans bike a Mk3 or is it an earlier one using the CNW conversion kit? How many starts has Alan clocked up since it was fitted?

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Mk2.

I dont know. A fair few. He has been to the South Island at least once, and across the North Island a couple times just for our rallies.

dobba99 said:

I would not take anything this 'tech' has said, as being a Cross and Morse recommendation.
Take a look at this, copied from the Cross and morse website https://www.crossmorse.com/images/specifications/Sprag_Elements.pdf
The import stuff is on the twelfth line onwards:- 'The sprag element is designed to rotate with the outer housing, this being essential for correct operation of the unit'

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While i understand the sprags may have been designed for use our way, the email came from a Cross Morse employee and email.

I am not trying to argue that they are the best option, I am just sharing what info I have at hand. Everyone makes their own bed.

dobba99 said:

I,m interested. Is Alans bike a Mk3 or is it an earlier one using the CNW conversion kit? How many starts has Alan clocked up since it was fitted?

Click to expand...

gortnipper said:

Mk2.

I dont know. A fair few. He has been to the South Island at least once, and across the North Island a couple times just for our rallies.

Click to expand...

Many thanks for that. It would be helpfull if all the Cnw estart kit owners kept a tally of how many starts their sprags clock up before failure and more importantly, how many miles the bike had done.
This photo was sent to me showing the wear (arrowed) on a ringspann sprag that had been fitted to a cnw kitted bike. Apparently this was the second ringspann to fail. Note the flat the arrow is pointing at.
With the 'heel dragging' problem in the CNW conversion kit it is the miles that the bike does that determines how the sprag wears. From one extreme to the other, you could do hundreds of starts and cover no miles, this would hardly wear the sprag at all.
At the other end of the scale, you could cover thousands of miles with very few starts (interstate tank, single carb!) and severly wear the sprag.