MK3 starter wont engage.

Good morning,
MKIII starter is not turning over the engine. I just replaced the sprag one way clutch. It started great on the first dozen times. So after pulling the cover this is what I came up with, here is info from Andover. The drive gear only .002 out of spec. I don’t know if that is enough to not allow to engage the sprag. The new sprag gear has 18 teeth, old one has 14, I replaced the old sprag because of a small crack, although its been in the bike this was for 8 years. I also read roughing the gear where the sprag gear meets works.

Thanks in advance.

.

I'm not plugging CNW in any way , but those parts come hardened with better tolerances .
Over 1500 starts after fitting the kit and very happy , no issues .
Won't start is a sad statement , electrical connections corroded or burnt could be the reason too , you seem focused on the mechanical .
Does the solenoid work ?

MS850 said:

Good morning,
MKIII starter is not turning over the engine. I just replaced the sprag one way clutch. It started great on the first dozen times. So after pulling the cover this is what I came up with, here is info from Andover. The drive gear only .002 out of spec. I don’t know if that is enough to not allow to engage the sprag. The new sprag gear has 18 teeth, old one has 14, I replaced the old sprag because of a small crack, although its been in the bike this was for 8 years. I also read roughing the gear where the sprag gear meets works.

Thanks in advance.

.

Click to expand...

You say it won't turn over the engine but don't describe the symptoms.
Is it:
* making a clattering sound?
* just whirring?
* electric motor not turning at all?
* something else?

A bit hard to advise without some extra info.
Cheers

The 14 tooth sprag that you removed, what does the 'crack' look like? some sprags had a bit of the cage that was made with a section that is only solid on one side and this section looks like it is there to hold the sprag in place. A lot of owners have seen this, thought it was cracked, and taken fright that their sprag is about to let go.
Just replacing the sprag with another is a bit of a lottery. AN recommend that the sprocket, sprag and drive gear are replaced as a whole.
CNW similar approach, replace with all their items.
You can use a cheap chinese sprag and hope this works (i used one for the last three years) till last month when it disintegrated and locked the drive to the engine, took out the starter as well....
If you have the facilities (or know someone who has) you can close the clearances up in the assembly by sleeving the drive gear snout (that sits inside the sprag). I use either an inner race from a needle roller bearing machined to fit, or an inner race from any scrap bearing that has a suitable size. These can be machined with sharp carbide tools. This was first outlined in Roadholder by a chap called Ken Merrick. He used loctite to attach the sleeve. I do it by an interference fit.
Your .002" out of spec sprocket, will be making the dogbones in the sprag sit at a more upright angle, which is bad (a greater danger of the sprag flipping) But to 'flip' it has to engage in the first place. As the sprag revolves around the drive gear (it stays in the same place in the sprocket when assembled) you can abrade the polished drive gear snout (plug the needle roller bore first) with some rough emery tape, don't go round and round with the tape, which is easy, you need to go along the axis of the drive gear with the tape (much harder to do) This finish will promote the drive gear to grip the sprag.

Thanks for the responses. I just received all the starter gear parts, Andover parts. Drive sprocket, sprang and starter ring gear.

Torontonian said:

I'm not plugging CNW in any way , but those parts come hardened with better tolerances .
Over 1500 starts after fitting the kit and very happy , no issues .
Won't start is a sad statement , electrical connections corroded or burnt could be the reason too , you seem focused on the mechanical .
Does the solenoid work ?

Click to expand...

I changed the material to a tougher core material with hardened case way back in 2016 long before CNW, they are also now ground to tolerance of .001's of a mm which is pain. 0.002'' is a massive out of tolerance when dealing with the mating parts even for the original system. The 14 and 18 sprags work in different working envelopes, but the tolerances if lucky could overlap with each other.
As above, the electrical side must be in very good working order and that applies to any electric start system.

FYI the sprag will slip and not grab if over oiled or greased

Madnorton said:

I changed the material to a tougher core material with hardened case way back in 2016 long before CNW, they are also now ground to tolerance of .001's of a mm which is pain. 0.002'' is a massive out of tolerance when dealing with the mating parts even for the original system. The 14 and 18 sprags work in different working envelopes, but the tolerances if lucky could overlap with each other.
As above, the electrical side must be in very good working order and that applies to any electric start system.

Click to expand...

Whatever .. Just buy the CNW kit and all your problems will be over .

I'm not familiar with your parts , but is the sprag the right way around .

I'm assuming from the comments above that the problem is in the over-running assembly and not electrical but you know what they say about the word assume. So. In my experience with these gizmos on both Norton and Royal Enfield I've found that the function of the sprag assembly is more dependent on the "dog bones" in the sprag than on the inner or outer races. If the surface of the dog bones is worn they will not stand up and will slip. If they eventually flip over, the un-worn side will now grab with disasterous results. The torque-limiter/anti-backfire device will prevent the flip over if adjusted correctly. Make sure it works properly.

I have installed new sprags in somewhat worn races with no problem. When the races get chewed up by a failure then they must be replaced. I believe most failures come from wear from swarf from the primary chain, clutch, etc. Frequent oil changes of the primary oil will forestall sprag wear. I suppose the races wear too but I can't believe that 0.002" out of spec would cause it to not work.

Using all new parts is expensive but should solve the problem. Just make sure the torque limiter works. Check it with a torque wrench.

The working envelope spec is online, no secret, from that you will see that 0.002'' is massively out of spec for a sprag - the tolerance is well tight.
Does electrical matter, yes, if the system does not spin fast enough it will not engage the sprag correctly.

Madnorton said:

The working envelope spec is online, no secret, from that you will see that 0.002'' is massively out of spec for a sprag - the tolerance is well tight.
Does electrical matter, yes, if the system does not spin fast enough it will not engage the sprag correctly.

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Faster the spin up the better . The sprag needs to splay outwards to grab , but fast .

The sprags engagement with the drive gear is where the 'grab' takes place (and where the slipping or 'non-engagement' happens), so the sprags action is 'inward' to grab the drive gear. The sprag revolves with the engine sprocket and when the engine is running centrifugal force throws the dogbones outwards slightly so they don't wear against the drive gear spigot. But yes, the faster the spin the better.

jimbo said:

FYI the sprag will slip and not grab if over oiled or greased

Click to expand...

That's right!
I fitted a CNW mk3 EA kit and stopped working after 10 starts!

I though i have thrown my money...

In the middle of my desperation i dismantled everething cleaned leaving a very light coat of wd40 which i more o less removed with a paper prior fitting everything back.


I filled 200 cc of Castrol Power1 10w40 wich has the JASO MA2 certification and problem solved.

The first oil i used was car oil, long life, not compatible with dry or wet clutch systems, the sprag has to brake the light oil film to engage in the same way as a clutch plates needs it, so apart from the viscosity i found very important to meet the JASO MA2 certification for the oil to be used.

I wished somebody had told me as i never read about this recommendation before.

Regards
Antonio

NorCat said:

That's right!
I fitted a CNW mk3 EA kit and stopped working after 10 starts!

I though i have thrown my money...

In the middle of my desperation i dismantled everething cleaned leaving a very light coat of wd40 which i more o less removed with a paper prior fitting everything back.


I filled 200 cc of Castrol Power1 10w40 wich has the JASO MA2 certification and problem solved.

The first oil i used was car oil, long life, not compatible with dry or wet clutch systems, the sprag has to brake the light oil film to engage in the same way as a clutch plates needs it, so apart from the viscosity i found very important to meet the JASO MA2 certification for the oil to be used.

I wished somebody had told me as i never read about this recommendation before.

Regards
Antonio

Click to expand...

I use 20/50 W. as recommended by the manual . Never a slip .

NorCat said:

That's right!
I fitted a CNW mk3 EA kit and stopped working after 10 starts!

I though i have thrown my money...

In the middle of my desperation i dismantled everething cleaned leaving a very light coat of wd40 which i more o less removed with a paper prior fitting everything back.


I filled 200 cc of Castrol Power1 10w40 wich has the JASO MA2 certification and problem solved.

The first oil i used was car oil, long life, not compatible with dry or wet clutch systems, the sprag has to brake the light oil film to engage in the same way as a clutch plates needs it, so apart from the viscosity i found very important to meet the JASO MA2 certification for the oil to be used.

I wished somebody had told me as i never read about this recommendation before.

Regards
Antonio

Click to expand...

Bad news, the system is not working, so it was not the oil, Matt will revert with good news soon.

NorCat said:

Bad news, the system is not working, so it was not the oil, Matt will revert with good news soon.

Click to expand...

Mmmm, seems that the CNW bits can exhibit the same symptoms as any of the other MK3 starter stuff available. If the sprag is not engaging try the emery tape method outlined earlier to remove the polished finish (drive gear snout too polished)

dobba99 said:

Mmmm, seems that the CNW bits can exhibit the same symptoms as any of the other MK3 starter stuff available. If the sprag is not engaging try the emery tape method outlined earlier to remove the polished finish (drive gear snout too polished)

Click to expand...

I think that I have to wait for their response, Matt knows there is a problem and is on it.

The Andover Norton parts work, for a limited time and expect CNW parts to be better once in the right direction.

I have faith on CNW knoledge and his commitment to Norton commando has been more than proven.

We have sprag bearings at work and if you hold the sprocket in your hand and turn it , what you think is right will be wrong , Is the sprag the correct way around ?