[tooseevee]

2CV
Did you replace the sprag assembly because of failure , or did you replace it to prevent a failure?

           Here's what happened:

           First just a little bit of background history.

           I got the '08 brand new in 2010 with zero mileage from an out-of-business dealer. It was drained, no battery & had just sat there. I got it with the original CMW title.
 
           I knew from the beginning the the ES was dodgy because of earlier research & from all the guys who had them here on the forum. So I avoided the ES & used the kicker most of the time during the years I spent learning about the bike & doing the many, many mods that I did. I worked & tweaked way more than I rode it. Plus my physical problems also dictated how many hours I could spend any given day tweaking OR riding. Many riding hours went down the shitter just learning & dialing-in the TM 32.

           One of my mods was getting rid of the huge battery & battery bracket. I always planned on using the kicker exclusively anyway so I got a small Motobatt that fit into the right side case (I had an Ace canister). I found that I could get 5 starter motor starts from this battery if necessary like if I stalled it at a stoplight. I was tweaked in by then & the bike had been a 1 or 2 kick starter so I didn't worry at all about using the ES once in a very blue moon.

            So we fast forward to May 2021. I had been putting together notes for my son who was to get the bike when I and he were ready for him to take it. He is not a kick starter person so I wanted to test the battery once again so I could warn him not to think he could ride all over town in a given day using the ES a lot. "You can get this much, but don't push it. Learn to kick it"!

            What I did was ES it, wait 5 minutes & then start it again. The first 4 went perfectly fine. Started instantly as it always had. The 5th start was the "straw". The sprag detonated, with a horrendous clash, as if a wrench had been thrown straight into the rotating gears.

            Once I got the primary off I found that everything was jammed up solid as a rock. Nothing would rotate in the slightest & it took a lot of figgerin' & prying with various tools of mass destruction to get the driving gear free from the driven gear so that finally the chain would rotate.  Finally got the inner primary off with the now loosened gears & there were pieces all over the place. When these things let go they really let go.

             I spent a long time on getting her back together very carefully & methodically. It's a very straight forward job, but it was divided into many steps, one step a day, as I could only spend at the most a half hour on the floor any given day & I tend to second-guess myself now too much. It works perfectly now & is a vast improvement over the original. It starts instantly & also shuts down instantly with no hint of any shutdown kickback (I have no decompressor so I shut down with the key).

             I'm glad it happened to me, not to Eric.

             

             
   

               

[SteveThackery]

It starts instantly & also shuts down instantly with no hint of any shutdown kickback (I have no decompressor so I shut down with the key).       

Now that's very interesting, because every bike I've ever owned did a shutdown kickback, where you can here it kick the starter which then runs backwards for half a second or so.

I only ever own singles or twins, so that might be relevant - big cylinders are more likely to kick back as they bounce off compression. My 350 Meteor and my Mandello both do it. I'd love to know why yours doesn't do it.

[tooseevee]

Now that's very interesting, because every bike I've ever owned did a shutdown kickback, where you can here it kick the starter which then runs backwards for half a second or so.

I only ever own singles or twins, so that might be relevant - big cylinders are more likely to kick back as they bounce off compression. My 350 Meteor and my Mandello both do it. I'd love to know why yours doesn't do it.

           Yes. That was one of the happy surprises about the whole thing & I can contribute it only to the new sprag which as I've said before, is a beautiful piece of engineering. It felt good in my hands just to turn it & then reverse it. No sound, no slack anywhere, it just STOPS dead.

            Like you say, previously to this, when I would shut down with key, I would get that little kickback, however slight, almost every time. Now there is Zeerow kickback. The engine just stops dead. Another thing I've never done is give the engine that "last rev up" before shutoff like a lot of guys do. Never did. Just let it idle & shut it off.

           It might be my imagination, but it also seems to crank more better for those 2 seconds that it cranks before it starts. I still use the kicker after it's warm.  The only other change I have to the cranking system is that I added a relay between the starter button & the OEM starter relay (years ago). The button seems very positive & should arc much less over the years.

[SteveThackery]

           Yes. That was one of the happy surprises about the whole thing & I can contribute it only to the new sprag which as I've said before, is a beautiful piece of engineering. It felt good in my hands just to turn it & then reverse it. No sound, no slack anywhere, it just STOPS dead.

I don't think changing the sprag clutch can stop it kicking back. The kick back is caused by a cylinder bouncing back off compression. I don't see how the sprag clutch can stop that regardless of how well engineered it is.

I'm inclined to think it's one of those fortuitous mysteries that happen sometimes. 

[Adrian II]

Take it as a win.

A.

[tooseevee]

I don't think changing the sprag clutch can stop it kicking back. The kick back is caused by a cylinder bouncing back off compression. I don't see how the sprag clutch can stop that regardless of how well engineered it is.

I'm inclined to think it's one of those fortuitous mysteries that happen sometimes. 

       Now that I think about it, you are correct. I was thinking about it wrong(ly).       

[REpozer]

           Here's what happened:

           First just a little bit of background history.

           I got the '08 brand new in 2010 with zero mileage from an out-of-business dealer. It was drained, no battery & had just sat there. I got it with the original CMW title.
 
           I knew from the beginning the the ES was dodgy because of earlier research & from all the guys who had them here on the forum. So I avoided the ES & used the kicker most of the time during the years I spent learning about the bike & doing the many, many mods that I did. I worked & tweaked way more than I rode it. Plus my physical problems also dictated how many hours I could spend any given day tweaking OR riding. Many riding hours went down the shitter just learning & dialing-in the TM 32.

           One of my mods was getting rid of the huge battery & battery bracket. I always planned on using the kicker exclusively anyway so I got a small Motobatt that fit into the right side case (I had an Ace canister). I found that I could get 5 starter motor starts from this battery if necessary like if I stalled it at a stoplight. I was tweaked in by then & the bike had been a 1 or 2 kick starter so I didn't worry at all about using the ES once in a very blue moon.

            So we fast forward to May 2021. I had been putting together notes for my son who was to get the bike when I and he were ready for him to take it. He is not a kick starter person so I wanted to test the battery once again so I could warn him not to think he could ride all over town in a given day using the ES a lot. "You can get this much, but don't push it. Learn to kick it"!

            What I did was ES it, wait 5 minutes & then start it again. The first 4 went perfectly fine. Started instantly as it always had. The 5th start was the "straw". The sprag detonated, with a horrendous clash, as if a wrench had been thrown straight into the rotating gears.

            Once I got the primary off I found that everything was jammed up solid as a rock. Nothing would rotate in the slightest & it took a lot of figgerin' & prying with various tools of mass destruction to get the driving gear free from the driven gear so that finally the chain would rotate.  Finally got the inner primary off with the now loosened gears & there were pieces all over the place. When these things let go they really let go.

             I spent a long time on getting her back together very carefully & methodically. It's a very straight forward job, but it was divided into many steps, one step a day, as I could only spend at the most a half hour on the floor any given day & I tend to second-guess myself now too much. It works perfectly now & is a vast improvement over the original. It starts instantly & also shuts down instantly with no hint of any shutdown kickback (I have no decompressor so I shut down with the key).

             I'm glad it happened to me, not to Eric.
             

Beatifically stated and helpful, thank you!
I still have the original working electric starter " sprag" system . I have been careful over the years. Its probably still a matter of time for it to eventually fragment itself. I will try to make it through the summer and  then put " sprag assembly " replacement on my next year winter to do list.

[tooseevee]

I don't think changing the sprag clutch can stop it kicking back. The kick back is caused by a cylinder bouncing back off compression. I don't see how the sprag clutch can stop that regardless of how well engineered it is.

I'm inclined to think it's one of those fortuitous mysteries that happen sometimes. 

       Ya' know, since my last post I've been thinking about this a lot & now I'm very, very cornfused.

        If the kickback isn't driving the sprag gear back into its "I can't rotate in that direction" direction then why do they detonate ? I'm just not seeing what's happening, I guess. I've tried to picture what is happening with the gears in both directions (the starting direction & the kickback direction) & I just can't get it.

        Why does a sprag destroy itself if it isn't being forced backwards against its locked direction (the direction it's going when the starter cranks it)?

        I've gotta find an animated illustration somewhere. It's driving me nuts.

        I thought the sprag clutch was supposed to prevent ANY CW rotation of the crank shaft, but I guess I've always had it wrong.

        Helllllp......

           

[AzCal Retred]

This is what I see as the sprag killer mechanism -

The sprag rollers turn freely when the crankshaft is turning CCW and the crankshaft speed exceeds the sprag speed.
The sprag rollers grip whenever the crankshaft is moving slower than the sprag or the crankshaft is turning CW.

The starter motor rotates the sprag CCW. The sprag locks up on the crankshaft and rotates the crankshaft CCW. The crankshaft then turns in the normal direction of running operation, CCW.

The starter motor is fairly power limited and takes a bit to wind up. The rotation it puts into the shaft happens fairly slowly in mechanical terms.

If the piston backfires, i.e. ignition happens before TDC, the crankshaft is driven very rapidly backwards (CW) by an impulse from an air/fuel explosion. The sprag locks up. The sprag then tries to instantly accelerate the mass of the starter motor. Apparently the OEM sprag assembly is the weakest link in the chain as it were.

My ES350 has worked flawlessly. It has a lot of flywheel relative to piston area. I don't recall ever having it kick back on start up even when manually booting it over.

My KS500  machine is a different animal. Even with mild 6.5/1 CR, proper timing & technique it'll kick back maybe once out of 5 tries. The 500 IMHO probably needs the Boyer electronic ignition if it has an electric start. The Boyer has an "extra retarded" function below 500 RPM. Your Orthopaedic Surgeon will thank you.

[SteveThackery]

This is what I see as the sprag killer mechanism -

Totally agree. I will add the other mechanism that happens on all bikes with big cylinders...

It's when you switch them off, not when you start them. The engine is idling, running CCW as normal. The sprag clutch is free-wheeling, so not turning the starter. When the ignition is switched off the engine slows to a stop. Usually, but not always, it stops when one of the pistons bounces back off compression, so the crankshaft runs backwards (CW) briefly. This drives the sprag clutch backwards, into engagement, which then spins the starter backwards, making the characteristic "whizz" sound. The sudden torque reversal is what is said to damage the sprag clutch. The advice to avoid this damage is to stop the engine with the decompressor, so it doesn't bounce back.

HOWEVER, I am sceptical. It isn't clear to me why engaging the sprag clutch during a bounce-back is any worse than engaging it normally by energising the starter motor. I suspect that the original sprag clutch simply isn't up to the job and will eventually fail anyway.

To be clear: bounce-back is extremely common on all sorts of bikes, but I've never owned a bike that wrecked its sprag clutch.

[Adrian II]

My understanding is that the IB and Electra-X/AVL sprag clutch is based on a Borg Warner item, which was presumably manufactured under licence in India. Metallurgy again?

A.

[tooseevee]

Totally agree. I will add the other mechanism that happens on all bikes with big cylinders...

It's when you switch them off, not when you start them. The engine is idling, running CCW as normal. The sprag clutch is free-wheeling, so not turning the starter. When the ignition is switched off the engine slows to a stop. Usually, but not always, it stops when one of the pistons bounces back off compression, so the crankshaft runs backwards (CW) briefly. This drives the sprag clutch backwards, into engagement, which then spins the starter backwards, making the characteristic "whizz" sound. The sudden torque reversal is what is said to damage the sprag clutch. The advice to avoid this damage is to stop the engine with the decompressor, so it doesn't bounce back.

           Thanks to you & AzCal I see it more clearly now. I wasn't confused about how the sprag works; I understand all that.

            What I was confused about was what gear was turning in what direction and when it was it turning.

            What I also wasn't seeing is that the starter motor also was being forced to turn backwards during a kickback.

             It's' all as clear as mud now, but it covers the ground 

[REpozer]

Are you all still dumping a full quart / litre of oil into the primary drive ?

I drained a quart/litre of ATF type " F" from the primary , and refilled with a quart/ litre of 15w-40 motor oil.

[African Boy]

Eventual was able to open up the the case . The sprag clutch I bought off Ebay is incorrect the part shown on Hitchcocks stated part number 560011 , the one I bought on Ebay said it was a direct replacement for 560011 ?  However I think the original part number should be #15 560042 it's held in with a circlip . Thanks for all your help guys .

[Paul W]

I drained a quart/litre of ATF type " F" from the primary , and refilled with a quart/ litre of 15w-40 motor oil.

The manual states that only 0.44 US Quart/ 0.42 litre is needed.