Mk3 Primary

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You'll be mighty unlucky if the clutch chainwheel needs replacing.... but expect everyone to be screaming CNW as soon as you mention new parts.
You will need the diaphragm tool though for any work, as both engine sprocket and clutch need removing for primary chain replacement..
 

L.A.B.

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I don't get any strange grumblings or scraping from the chain case, but I will do 50 miles tomorrow and then look inside the case again at the weekend. I'll check the tensioners. If they look ok and the chain is still very loose, time to spend again.

I still don't think you completely understand how the tensioner operates?
The tensioner doesn't 'ratchet' to take up slack as the chain wears, therefore, if you push/pull on the chain run then the amount of movement could be interpreted as the chain being 'loose' becasuse the chain is only under tension from the relatively light plunger springs.
If, as you said, the chain doesn't appear as worn as the one in my previous photo and can't be made to touch the case, then I don't think you have anything to worry about.

If I stay with the stock set up, and replace the primary chain, sprag, do I also need items 19 and 21 (starter drive gear and thrust washer) in this drawing? https://andover-norton.co.uk/en/shop-drawing/133/electric-start# Do I also need the needle bearing (item 20)?

'19' = If the sprag track on the gear is in any way worn or 'dimpled' (as dynodave describes it) then yes.
'21' = No.
'20' = If you fit a new '19' gear then probably wise to fit a new bearing. The bearing inner race is item '22'.

To replace the primary chain, do I need to replace the triple sprocket: item 32 here: https://andover-norton.co.uk/en/shop-drawing/132/gear-linkage-chains-alternator-engine-sprocket#

If you intend to replace the sprag assembly then the engine sprocket '32' will be one of those items.


And item 2, clutch chain wheel, here: https://andover-norton.co.uk/en/shop-drawing/130/clutch, or, if they look OK, leave them in place?

Depends on its condition.


Whilst there, I'll look at the tensioners / check for gasket. Anything else I should check / be sensible to replace?

I will read through the shop manual, NOC's service notes etc. And go step by step. If i have to replace the clutch chain wheel, I'll also need to buy the clutch tool. Any other special tools /anything else to be wary of?

I think perhaps you could be worrying unnecessarily about the condition of the chain.
The engine sprocket contains the outer sprag track which is why that part is more likely to need replacing.
The clutch tool is something every Commando owner ought to have and if you open up the primary again then I suggest you use it to clean the clutch plates (especially if the clutch has the original bronze friction plates) and to check the condition of the clutch centre splines for notching.
 
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The MK3 has fixed centres so the chain slack is not a direct indicator of wear, as its not hitting the cases with the tensioner deployed this confirms it isn't worn. The definitive measure of wear on a chain is the distance between the pins, if you measure the length over say 10 pins with an accurate caliper and compare the length with a new chain. If the wear shows as being 1% I would fit a new chain, this will preserve the sprockets as they wear quicker with a worn chain.

 
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Steven
Where did you get the 300cc spec?
The shot below (I've left enough pics so you can see it's for Mk3) is from the "Commando - Norton Riders Manual - 850 MkIII Models" and it clearly states "7 fl.oz. (200)cc of fresh oil. be careful not to overfill"
View attachment 78873
300cc is not a written spec. The manual states to "fill to the level plug hole." If you fill a MK3 primary to the oil level hole, it takes ~300 cc's.
So why would the fill level hole be volume be 300 cc's and the manual spec be 200 cc? I suspect that when they changed the MK3 outer primary case design to accomodate the starter, sprag and hydraulic tensioners, and like other manual errors, they never changed the pre-MK3 200cc spec in the manual.
I used a borascope to look into the case at 200 cc's and at the fill hole level (~300 ccs). At 200 cc's the oil level is well below the chain. At the fill hole level (~300ccs) it is just below the chain. The chain and the clutch basket throw oil to fill the chain tension catchment as well as lubricate the sprag, etc.
To follow the manual you can either fill to the oil level hole or just put in 200 ccs. I fill to the oil level hole assuming they designed the fill level hole correctly.
Cheers
 
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Steven,
In Section A, Capacities, the Mk III Workshop manual does call for 200cc of oil. However, that is just another of the many errors. This info was simply copied over from the earlier manuals without change. Something that is done in a number of places in the manual.
Section C34, Step 37 simply states to refill the primary, with no mention of method or amount. However, Section K9 clearly describes filling to the level plug, as you have outlined above. I'm going to correct that 200cc statement in Section A of my edited Mk III workshop manual.
It stands to reason that the Mk III primary case will require more than the 200cc called out for earlier primary cases, as the longer crankshaft and added starter motor drive gear required a pair of wider primary drive cases.
Sections K2 & K3 state that the primary oil is to be changed every 3,000 miles.
Just saw your post. Sorry to be repetitive. Cheers
 
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Do not think the oil level in primary is the cause of problems with the starter system on an MK3.
I am convinced that the causes of errors are too poor design and or poor quality of the parts.
Think this discussion has taken a wrong direction.
Vidar
 
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Do not think the oil level in primary is the cause of problems with the starter system on an MK3.
I am convinced that the causes of errors are too poor design and or poor quality of the parts.
Think this discussion has taken a wrong direction.
Vidar
No one said the oil level was an issue with the starter. The oil level relates to proper oiling of the chain and keeping the reservoir in the chain tensioner system properly supplied.
 
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The MK3 has fixed centres so the chain slack is not a direct indicator of wear, as its not hitting the cases with the tensioner deployed this confirms it isn't worn. The definitive measure of wear on a chain is the distance between the pins, if you measure the length over say 10 pins with an accurate caliper and compare the length with a new chain. If the wear shows as being 1% I would fit a new chain, this will preserve the sprockets as they wear quicker with a worn chain.

So true. I recently compared a worn primary chain to a new one (as purchased new) and the suspected worn one was indeed about a half inch longer or so. I laid them beside each other and pulled lengthwise to each to take up the/any slack. The difference was noticeable and tossed the quite old one immediately into recycling. ( we have a state of the art recycling facility here ) .
 
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You will need the engine sprocket extractor tool which can either be bought separately or as part of the 06.4297 extractor 'kit'.
MK 111 uses a puller with 4 " bolts.
All previous models use the two 3" puller bolts.
They should be hardened . Grade 8.
 

L.A.B.

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MK 111 uses a puller with 4 " bolts.
All previous models use the two 3" puller bolts.


The same extractor part number (064297) is quoted in the pre-Mk3 manual and the only Commando engine sprocket extractor AN sells, therefore, the longer bolt extractor can be used for pre-Mk3.
 
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To replace the primary chain, do I need to replace the triple sprocket: item 32 here: https://andover-norton.co.uk/en/shop-drawing/132/gear-linkage-chains-alternator-engine-sprocket# And item 2, clutch chain wheel, here: https://andover-norton.co.uk/en/shop-drawing/130/clutch, or, if they look OK, leave them in place?

Whilst there, I'll look at the tensioners / check for gasket. Anything else I should check / be sensible to replace?

I will read through the shop manual, NOC's service notes etc. And go step by step. If i have to replace the clutch chain wheel, I'll also need to buy the clutch tool. Any other special tools /anything else to be wary of?

Thanks,

Mart
Just in case you dive in to removing the engine sprocket and as others have said already, the Mk3 sprocket puller requires longer bolts. I recently faced this issue and didn't have the Norton puller so bought some 4.5" long bolts from McMaster-Carr (https://www.mcmaster.com/91257A443/) to use with my existing puller. The extra half inch provided a little more space for me to insert a sacrificial soft steel pad on the end of the crankshaft. It took a lot of force to break that sprocket loose. I heated the sprocket using a small heat gun zip-tied to a suitable box spanner placed over the crank. I left that thing running for about half an hour and then pre-tensioned the puller and following the advice of the shop manual "shocked" it loose with a brass drift and ball-pein hammer. I was mighty relieved when it popped off cleanly. The heat gun didn't get it too hot, just hot enough. It's also a good idea to lightly grease the threads of the puller; you get more pull for your torque that way. Good luck!
 

Mart UK

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I did a short ride yesterday, after which it no longer starts on the starter. Just quietly spins, without any clatter. So, it seems I'm going to have to replace the sprag mechanism. I'll go back through the above advice and order the parts.
- I will leave the primary chain in place. It is not touching the chain case and looks OK. I'll clean it in situ
- I will remove and clean the tensioners and re-prime them and put a fresh gasket on
- I will leave the anti-backfire alone
- I'm not sure about the clutch. I expect I should dismantle and clean it?

No special tools, unless I remove the clutch? Should I do that? It is quite a stiff action, so I should probably inspect the splines for any burrs. But I'm a bit wary of messing with the adjustment.

Thanks, Martin
 

L.A.B.

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I did a short ride yesterday, after which it no longer starts on the starter. Just quietly spins, without any clatter. So, it seems I'm going to have to replace the sprag mechanism. I'll go back through the above advice and order the parts.
I suggest you check both sprag rings for cracks, also the condition of the spring between them as the tiny tabs that support the individual sprags can break off.

I will remove and clean the tensioners and re-prime them and put a fresh gasket on

Priming the tensioner only lasts until the oil drains out but a good idea to clean it and ensure the ball valve is clear and the ball moves freely but no need to remove the valve unnecessarily. Once primed you can check it operates correctly as pushing one plunger in should force the other plunger out.

I'm not sure about the clutch. I expect I should dismantle and clean it?

If it isn't slipping or dragging then there's no immediate need to do so, but it's one of those things that should be done periodically especially if it has original bronze friction plates as they tend to get a build-up of black gunge on the friction surfaces.

No special tools, unless I remove the clutch? Should I do that? It is quite a stiff action, so I should probably inspect the splines for any burrs. But I'm a bit wary of messing with the adjustment.

It's something you should consider doing some time in the future for the reasons stated.

A stiff action suggests the plate stack height is 'low' and probably could be improved by replacing one plain plate with either a 3mm or 4mm plain 'adjuster' plate...

...or an additional plain plate but I suggest you measure the stack height first before exceeding 3mm.

Whenever working on the clutch make sure the pushrod actuator inside the gearbox outer cover does not drop out of position as that will result in a very heavy clutch action until corrected.
 

brokeneagle

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This may have been addressed already, but the tolerance of wear on the the starter gear and the the sprocket that the sprag makes contact with is very tight. A couple thousands worn and a new sprag will be ruined in no time. If you need all three, the new CNW (John Snead) parts are very competitively priced IMO. Also this write up from Old Brits might shed some light.
 
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Hi,

I now have a few hundred miles on my new, to me, 850 Mk3. About 500 miles ago, the PO had a new sprag clutch and sprocket etc. I assume there was a failure. Lately, first start with the button, I just get a whirring. No clacking or grinding, just a spinning. Then it catches second attempt. It's also fine if I ease the motor past compression with the kickstart. I also have a healthy weep from the rear / bottom of the primary seal. I researched the primary and starter threads on here.

I drained the oil, it was dark, with a fine metallic content. Also, well below the drian plug level. I'd say c.200cc was in there. Being the hydraulic primary chain tensioner version, I think it should have more oil (to the level screw). Also the triplex primary chain looked quite slack. Just off the chaincase. I'm assuming that's because the hydraulic tensioners had bled down?

I am thinking:
- The anti backfire may not quite be torqued-up enough, causing the starter to slip;
- The metallic oil may be due to the previous sprag failure;
Reasonable?

I cleaned everything out. Read the Old Brits article on the anti-backfire adjustment, which put me off a bit. I don't weld and so don't have access to a tool for checking the backfire device torque setting. For the moment I've put a new (AN) gasket on, with Wellseal and put in enough oil to the level plug, leaving it a couple of hours, to make sure it wasn't still weeping (just over 300cc). I plan to run it for a hundred miles or so and then drop the oil again, to see if it is clean. I'm hoping there's nothing more sinister. Does that seem sensible?

I know the starter problem won't disappear on it's own, but want to solve one concern at a time. Assuming I'll still have the starter slipping problem, does the anti-backfire seem a sensible cause? How do you adjust yours to get it right? As I understand it, it is the nut on the spindle inside the alternator stator, that I need to adjust (tighten a touch)? Can I do this leaving the stator and everything in place in the Primary?

Thanks,

Martin
I was having a problem with the starter sprag not engaging on my bike, starter motor just spun and the engine did not. I had replaced the sprag not long ago, I asked our local Norton Guru what he thought. He said the battery was probably bad. It charged up OK, and showed no sign of being anything but good shape. I replaced it anyway, and the starter has work flawlessly ever since.
My chaincase cover seeps at the bottom middle screw hole. I put a small o-ring on that screw before threading it in, and stopped the leak.
Just my experiences.
 

Mart UK

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#Brokeneagle, useful link, thank you. I've noticed the parts diagram appears to depict the thrust washer part no.21 incorrectly: https://andover-norton.co.uk/en/shop-drawing/133/electric-start# The indent seems to be the wrong way round vs. the picture of the part and the old Brits notes?

#Darmah78, I swapped in a 3 month old 16.5Ah battery, with no improvement. I've had it on the tender overnight, so will give it one more try, before stripping down today.

Although money is a bit tight right now, I'd prefer to do this only once. So, I think I've got all the necessary parts and tools on order from AN. When I factor in delivery and customs, I'm looking at nearly £200 extra for CNW. So will give the 'stock' parts one chance! At least it is the 18 roller sprag, starter drive gear with new bearing and inner race and new thrust washer. I've decided to try to eliminate any likely cause of premature failure (only 500 miles on the current sprag), so, painful though it is, have included a new engine sprocket (which is advised) and primary chain £47. I also have a new gasket, so I can clean up the primary chain tensioners.

I will use the AN sprocket puller for the engine sprocket. Does this do the job, without the need for any heat or other persuasion? I assume I need to take it off and reassemble by removing the clutch chain wheel at the same time. Does that come off readily, without any puller? I'm assuming it must, so it doesn't interfere with the clutch movement on the shaft. I have the clutch diaphragm tool on order, to remove that and then the plates first, to thoroughly clean that up too. I'll check the factory manual torque settings with #Chaztuna's updated version he kindly emailed.

Should I apply any lubrication, or is it best to assemble the sprag and bearing dry on the crank?

Appreciate all the advice. Only a month into my first Norton, it's brilliant knowing the experience is out there to put me on the right track. Whilst I wish it hadn't failed, I'm looking forward to working on it!
 

L.A.B.

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I've noticed the parts diagram appears to depict the thrust washer part no.21 incorrectly: https://andover-norton.co.uk/en/shop-drawing/133/electric-start# The indent seems to be the wrong way round vs. the picture of the part and the old Brits notes?

Yes, the indents are drawn incorrectly but otherwise fits as shown with the shoulder to the outside (as I don't think the sprag would fit with it reversed).

I will use the AN sprocket puller for the engine sprocket. Does this do the job, without the need for any heat or other persuasion?

It's always worked for me without any heat but might need a few sharp blows with a good size hammer.
I assume I need to take it off and reassemble by removing the clutch chain wheel at the same time.

Probably.
Does that come off readily, without any puller?

Should do.

I'll check the factory manual torque settings with #Chaztuna's updated version he kindly emailed.

Yes, torque the clutch nut (with Loctite) to 40-50 lbs. ft. as it says in Chaztuna's manual, not the original factory manual setting of 70 lbs. ft. which can destroy the clutch location circlip (060752) behind the clutch.

Should I apply any lubrication,...?

Yes, apply a little primary oil (20W/50). The sprag should be lubricated by primary mist/splash.
 

Mart UK

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I was having a problem with the starter sprag not engaging on my bike, starter motor just spun and the engine did not. I had replaced the sprag not long ago, I asked our local Norton Guru what he thought. He said the battery was probably bad. It charged up OK, and showed no sign of being anything but good shape. I replaced it anyway, and the starter has work flawlessly ever since.
My chaincase cover seeps at the bottom middle screw hole. I put a small o-ring on that screw before threading it in, and stopped the leak.
Just my experiences.
So,
Lined my tools up, oil catch can ready for the dress down and remembered this post. Thought, why not. Took the replacement battery now on the bike, off the tender and you can guess the rest. Started like a dream. I thought probably a fluke. With rests in between, 10 attempts, 9 successes, 1 whir. What to do?

I guess I'll watch it and see if it comes back. Seems too good to be true, so probably is, but seems masochistic to break into it right now. New oil in the primary (again). Will report back.
 
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What to do? Start a: How do I uprate the charging system/What's the best battery' thread :)
Or simply ride it!!!!!!
The joys of Norton pet ownership.....
(Does it start OK on the kickstart?)
 
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