MkIII Electric Leg Questions

Trying to help out new owner of a MKIII bike with non- working e-start. He was back from a ride recently and engine was shut down when tweaking with the throttle stop screw on one carb...said it stopped with a backfire event. But I think that is unrelated. Upon trying to restart, starter just whirs with no engagement of engine crank. Is that typically the sprag clutch gone?
Today I visited to see it firsthand. We attempted to remove primary cover but a few of the fixing screws were too tight for the tools at hand...needs a heavy duty impact driver with a B.F. hammer I think, maybe some heating to soften any locktite in use.

Cannot kick start as the kicker does not seem to engage at the pawl device...I could hear/feel ratchet trying to engage, but will not hold any force off the kicker.

Another issue noted, the gear change shaft wobbles about where it passes out of outer primary. I assume there is a bush that can be replaced there?

Finally, I noted the throttle grip fairly stiff to rotate. My mkII bike has a slotted head bolt to tighten/lock grip, his mkIII has a much thinner slotted set screw with a fixing nut. We could not slacken that off as it was taking too much force and didn't want to risk damaging the slot. Any tricks here?

Sounds like the anti backfire device needs to be check to see if it is opperating correctly, and and the sprag let go. I would highly recommend upgrading the sprag bearing and gears. While you are at it get the Dyno Dave starter. I did this 10 years ago and it still runs strong. The dyno dave starter was a later discovery and the best money spent on the bike.

Sounds like the sprags may have rolled over. That is a common failure mechanism in sprag clutches, and usually ruins the unit. Failure of the sprag clutch will also mean the kicker no longer works. You'll have to pull the primary apart to find out for sure.

Ken

lcrken said:

Sounds like the sprags may have rolled over. That is a common failure mechanism in sprag clutches, and usually ruins the unit. Failure of the sprag clutch will also mean the kicker no longer works. You'll have to pull the primary apart to find out for sure.

Ken

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In this bike kicker has not worked in some time, while sprag was fine until last week. When I pushed kicker by hand, almost zero resistance. And could feel the pawl trying to engage but never did. Just a ratcheting feel/sound from gb.
So I think two different problems.

Same symptom as when my sprag failed.

I was told it is best to replace everything in direct contact with the sprag. CNW do an upgraded version, which looks nice, but expensive. I went with Andover Norton's parts. Fine so far after 3 years and probably over 100 starts.

Good opportunity to check the chain tensioner is working. Mine wasn't and the chain rubbed the case which led to metal powder in the oil. I think this caused the sprag to wear and die.

As everything in the primary has to come out, it's a good time to change the seals and the drive chain front sprocket, if showing its age.

lcrken said:

Failure of the sprag clutch will also mean the kicker no longer works.

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This is not correct.

it’s needing to come apart in three areas so far….

Mart UK said:

Same symptom as when my sprag failed.

I was told it is best to replace everything in direct contact with the sprag. CNW do an upgraded version, which looks nice, but expensive. I went with Andover Norton's parts. Fine so far after 3 years and probably over 100 starts.

Good opportunity to check the chain tensioner is working. Mine wasn't and the chain rubbed the case which led to metal powder in the oil. I think this caused the sprag to wear and die.

As everything in the primary has to come out, it's a good time to change the seals and the drive chain front sprocket, if showing its age.

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Watched a detailed primary case rebuild video (Jesse's Vintage Garage channel) and it seems that to just change out the sprag only alt, alt mount bracket, rotor and the starter gear under rotor needed to come off to expose sprag. Is that correct? No need to completely pull rest of gubbins?

Will come down to what owner wants to afford. I've mentioned the AliExpress sprag some members here have good results with. If there is the other pieces inter mingling with sprag to change out to that will be quite a bit more than I may be able to do for him.

Tornado said:

Watched a detailed primary case rebuild video (Jesse's Vintage Garage channel) and it seems that to just change out the sprag only alt, alt mount bracket, rotor and the starter gear under rotor needed to come off to expose sprag. Is that correct?

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Yes.

I removed the clutch as well, so the primary chain could come off nice and square. There may be enough slack in an older chain, but mine only had 2,500 miles on it and wouldn't have come off just the front. At least, I don't think so.

Good opportunity to clean the clutch up. Mine had a lot of deep wear grooves, so I replaced that too.

L.A.B. said:

This is not correct.

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You are right. The sprags are not directly involved in the kick starting mechanical train. I stand corrected.

I have had the sprags roll over twice, on two different bikes. But the most recent was still quite a few years ago. I thought it had also affected kick starting at that time, but apparently it's just another memory moment.

Ken

If funds are limited, you could try replacing the sprag with the $17 Chinese version. They seem to be made a bit better than other replacement sprags in that they resist overcentering.

I'm still using mine and it's been in there for a few years now.
Inflation might have pushed the price up above $17 by now.

Glen

lcrken said:

You are right. The sprags are not directly involved in the kick starting mechanical train. I stand corrected.

I have had the sprags roll over twice, on two different bikes. But the most recent was still quite a few years ago. I thought it had also affected kick starting at that time, but apparently it's just another memory moment.

Ken

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With the first and second sprag failure on my bike kickstarting was not possible as the sprag cages broke and the rollers ended up jamming things.
I recall phoning my wife who brought tools to me so that I could pull the primary off roadside and remove the offending sprag bits. I was then able to kickstart the bike and ride it home. Perhaps you had a similar experience?

After the second UK sourced sprag broke I decided that the bike could be a kickstart bike for a decade or so. It's an easy starter so it wasn't a big issue. I finally decided to try one of the cheap Chinese sprags a few years ago.
This was before the uprated CNW MK3 starter parts were available.

Glen

On AN parts list from the mkIII starter, it shows the 18 roller sprag picture with a note overlayed thus:



Is it true that a 14 sprag setup must only be replaced with a 14 unless the other parts are changed for the 18 sprag?

worntorn said:

With the first and second sprag failure on my bike kickstarting was not possible as the sprag cages broke and the rollers ended up jamming things.
I recall phoning my wife who brought tools to me so that I could pull the primary off roadside and remove the offending sprag bits. I was then able to kickstart the bike and ride it home. Perhaps you had a similar experience?

After the second UK sourced sprag broke I decided that the bike could be a kickstart bike for a decade or so. It's an easy starter so it wasn't a big issue. I finally decided to try one of the cheap Chinese sprags a few years ago.
This was before the uprated CNW MK3 starter parts were available.

Glen

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Thanks for the info, Glen. It's frustrating to recall such incidents, but be kind of fuzzy on the details. I think my last instance was like yours, but just can't be sure.

Ken

I have been using an AliExpress sprag for close to 2 years, it is an 18 "tooth" and fitted straight in, I have another on the shelf just in case.

According to my maintenance book for the 850, this Aliexpress sprag was installed in 2017. I can't say exactly how many starts it has done as I only kept track to 500 starts, which occured after 3 or 4 years of use . This bike gets ridden a fair bit, so it's probably at a thousand or so starts on that sprag by now.

Glen

worntorn said:

According to my maintenance book for the 850, this Aliexpress sprag was installed in 2017. I can't say exactly how many starts it has done as I only kept track to 500 starts, which occured after 3 or 4 years of use . This bike gets ridden a fair bit, so it's probably at a thousand or so starts on that sprag by now.

Glen

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And to clarify, was it replacing original 14 sprag and installed alongside the original associated parts?

Yes, the bike is still using all original starter drive parts other than the sprag itself. I can't recall the number of rollers in the old sprag that failed or the new Norvil sprag that lasted one day.

Glen

worntorn said:

According to my maintenance book for the 850, this Aliexpress sprag was installed in 2017. I can't say exactly how many starts it has done as I only kept track to 500 starts, which occured after 3 or 4 years of use . This bike gets ridden a fair bit, so it's probably at a thousand or so starts on that sprag by now.

Glen

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