Mk3 Primary

Mart UK

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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?)
Groan. Not going to think about the charging system!

Kickstart: I'm 160lbs wet, with a dodgy right knee, sports injury. I can stand and bounce my weight on the kickstart without moving it. I have kickstarted it, but painful. Why I decided I needed a Mk3! I even make kick-starting an Enfield 500 look difficult... So kickstarting will be a last resort, if I get stranded. I can't believe it's sorted, but I will hope for now. I'll keep the parts and this afternoon am reading through the updated links from Chaztuna's corrected workshop manual, which he reminded me would be useful.

What can I say. Yesterday, it just whirred, today it works. The only difference is fully charging the replacement battery, which I hadn't used in anger and didn't work yesterday, when I swapped it, before I charged it overnight. Bit bemused, not yet relieved! My money would still be on a sting in the tail to come...
 
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snipped 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? snipped
Martin, Ride it. Sprag slippage may be caused by debris intermittently being caught between the front sprocket and the sprag. Perhaps change the primary oil at 100 mile intervals until it comes out completely clean. FYI, clean oil will also help to clean off those clutch plates. Might want to consider filling the primary temporarily with ATF, rather than 20W-50. ATF has an extremely high detergent package, so will do a better job of cleaning the clutch plates. FYI, ATF being thinner, tends to drain out of the hydraulic tensioning unit to fast for permanent use. Let the primary oil drain out over night when changing. Report back regarding if your clutch operation improves with cleaning out the primary, via oil changes. Cleaning via riding is much more fun than wrenching! ;)
Regarding the oil volume, are you filling it while on the side stand or center stand?
 
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You'll be mighty unlucky if the clutch chain-wheel 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..
Martin, you can save money making your own special tools. Several DIY low dollar clutch diaphragm spring tools can be found below:

Tools You Have Made
 
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snipped

What can I say. Yesterday, it just whirred, today it works. The only difference is fully charging the replacement battery, which I hadn't used in anger and didn't work yesterday, when I swapped it, before I charged it overnight. Bit bemused, not yet relieved! My money would still be on a sting in the tail to come...
The power tap, below the oil tank cover is a handy way to trickle charge your battery, without the need to disassemble things. FYI, NEVER charge a motorcycle battery at more than 10% of it's amp/hour [14 for a Mk III] rating. You can ruin a battery that way.
 

Mart UK

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Martin, Ride it. Sprag slippage may be caused by debris intermittently being caught between the front sprocket and the sprag. Perhaps change the primary oil at 100 mile intervals until it comes out completely clean. FYI, clean oil will also help to clean off those clutch plates. Might want to consider filling the primary temporarily with ATF, rather than 20W-50. ATF has an extremely high detergent package, so will do a better job of cleaning the clutch plates. FYI, ATF being thinner, tends to drain out of the hydraulic tensioning unit to fast for permanent use. Let the primary oil drain out over night when changing. Report back regarding if your clutch operation improves with cleaning out the primary, via oil changes. Cleaning via riding is much more fun than wrenching! ;)
Regarding the oil volume, are you filling it while on the side stand or center stand?
Well, I certainly hope that's the case. I'll change the oil regularly, ATF suggestion noted. I am letting it drain for a few hours, but overnight sounds good, after a ride. Filling it on the centre stand and it's 200cc, not 300cc as some have reported. It's the eleven screw case, so definitely a Mk3. On a level garage floor. The first flush I did was after cleaning inside with brake cleaner on a clean rag, but keeping clear of the sprag, clutch and tensioners, so will have left muck in there. But even after removing all obvious old oil, it still only took 200cc before it seeped out the level plug.
 
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Mart UK

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The power tap, below the oil tank cover is a handy way to trickle charge your battery, without the need to disassemble things. FYI, NEVER charge a motorcycle battery at more than 10% of it's amp/hour [14 for a Mk III] rating. You can ruin a battery that way.
I use a battery tender / conditioner unit, on the AGM motorcycle setting, so no danger of overcharging. I have the tails permanently on the battery, so I just plug it in.

Monitoring the tender's indicators, it's showing the new battery recovered much quicker than the previous one. Maybe the previous battery was on the way out, but it was a 12Ah, the new one is 16.5Ah. May just have lacked the punch to get the inial spin of the starter to catch the sprag, if the sprag springs are a little lacking? IDK how else to explain it, perhaps residual muck is working it's way out, as you suggest. I'll keep my fingers crossed and keep flushing regularly and see how it goes..
 

L.A.B.

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Sprag slippage may be caused by debris intermittently being caught between the front sprocket and the sprag.

Or the sprag tracks are worn (the sprag being relatively new) and the slippage will just steadily become worse.

Perhaps change the primary oil at 100 mile intervals until it comes out completely clean.

Not exactly necessary in my opinion as it's been mainly cleaned and there always seems to be some black residue in the bottom of the primary.

Might want to consider filling the primary temporarily with ATF, rather than 20W-50. ATF has an extremely high detergent package, so will do a better job of cleaning the clutch plates. FYI, ATF being thinner, tends to drain out of the hydraulic tensioning unit to fast for permanent use.

I found the Mk3 tensioner not to work anywhere near as well with ATF in the primary causing the primary chain to snatch badly at low speeds when I used it in my Mk3.
A better alternative in my opinion rather than trying to flush the plates clean with repeated oil changes (which I'm not sure actually works?) would be to remove the clutch plates and clean them. Then, the job is done.
 

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Filling it on the centre stand and it's 200cc, not 300cc as some have reported.

You probably won't get all the oil out using the drain plug as a certain amount will be trapped in the case by the screw tunnel...


...which extends across the full width of the primary case so the refill amount would be reduced and the drain plug hole in the background isn't at the lowest point either.
 
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Martin and other MK 111 owners. Pull in your clutch lever before pressing the starter button. When the bike starts up , release the lever. This puts less stresses on the sprag. Stick to 20-50 Weight oil as the manual says. The main shaft circlip should be replaced with one that does not crush. 06-8072 ( It will need some sanding down to become a bit thinner to tap into the slot ). 06-4989 is the original one that can crush. Another item that crushes is 06-3459 , tab washer. It should be upgraded . There are threads on this.
 

Mart UK

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Took it for a ride yesterday. Started first pull. Got home, drained the engine oil, new filter, cleaned screen etc. fresh oil. Went to start , to recheck oil level, just whirred, not engaging.
This afternoon, after a day on the battery tender, whirred first and second time, started third attempt. I can tell when it is going to start, there's a very slight dull thud as it finishes whirring round, like it has re-engaged.

Parts should arrive after the Easter break. Looks like plan A. As it seems to start better fresh from an overnight charge, vs. after a ride, I would also like to check all is OK with the alternator output. I don't really think there's a problem, but I'll check it, before I start on the primary.
 
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Took it for a ride yesterday. Started first pull. Got home, drained the engine oil, new filter, cleaned screen etc. fresh oil. Went to start , to recheck oil level, just whirred, not engaging.
This afternoon, after a day on the battery tender, whirred first and second time, started third attempt. I can tell when it is going to start, there's a very slight dull thud as it finishes whirring round, like it has re-engaged.

Parts should arrive after the Easter break. Looks like plan A. As it seems to start better fresh from an overnight charge, vs. after a ride, I would also like to check all is OK with the alternator output. I don't really think there's a problem, but I'll check it, before I start on the primary.
Sounds like your issue is that sometimes the starter is not spinning the drive gear fast enough to get the sprags in the sprag clutch to "lock in" to the ID of the crankshaft sprocket. You might want to consider contacting Dobba99 regarding his ball & needle bearing conversion. He reports that this improves the stock 2 winding starter speed, via friction reduction.

 

Mart UK

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Sounds like your issue is that sometimes the starter is not spinning the drive gear fast enough to get the sprags in the sprag clutch to "lock in" to the ID of the crankshaft sprocket.
Possibly. If so, there should be a reason for it?
Mechanically: I don't know if it can inhibit the operation of the sprag, but I plan to check the shaft for any roughness / obvious wear and am planning to replace the sprag, its bearing and inner race and the triple engine to primary chain sprocket, along with the primary chain. So, that should deal with any wear / failure. I'm also going to remove and thoroughly clean the contents of the primary, including the tensioners and the clutch, in case dirt and debris was inhibiting the sprag. I'll see if I can check alignment of the engine sprocket to clutch chain wheel, in case that's causing any distorting forces, but I'd have thought the primary chain would take that up and wear prematurely? However, I'd like to leave the anti backfire alone, to avoid messing with the torque setting, I don't have the tool fabrication skills needed for the Old Brits technique.

I'm not convinced that will sort it out, as the PO replaced the sprag in Feb and it's done just under 500 miles since. There may be an electrical weakness reducing the power of the starter / forces triggering the sprag engagement.

Electrically, I'll visually check starter earth and connectors, so far as I can. I'll also look at the alternator / stator performance, before I go into the primary case. The manual confuses me (introducing 1ohm resistance and only 9V AC @3,000rpm, which seems low). Also, I'm neg earth/ground and no zenor diodes (Boyer Powerbox). I'm used to a 3 phase stator, testing for c.0.3 - 0.5 kOhms consistent between terminals, >20V AC at tickover, 60 to 80V AC at over 4,000rpm. Post reg/rec, c.13V DC at battery terminals, tickover and >14V, <15V DC at >4,000rpm. Any reason these tests (and figures) aren't suitable on my Commando, just as a health check?

Thanks.
 

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Mechanically: I don't know if it can inhibit the operation of the sprag, but I plan to check the shaft for any roughness / obvious wear and am planning to replace the sprag, its bearing and inner race and the triple engine to primary chain sprocket, along with the primary chain. So, that should deal with any wear / failure.
Possibly the result of fitting a new sprag to old tracks so to fit yet another sprag is unnecessary.
The sprag "inner race" is part of the 06.4731 drive gear so to replace the inner track means replacing the gear.
est04.jpg
 
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Martin you may want to upgrade a couple of electrical cables to a thicker/ larger size.
One will be the battery ground.
The other more important one will be the starter motor to the solenoid switch.
These can be purchased pre-made if you don't feel like creating your own.
 

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Possibly the result of fitting a new sprag to old tracks so to fit yet another sprag is unnecessary.
The sprag "inner race" is part of the 06.4731 drive gear so to replace the inner track means replacing the gear

Yes, I am replacing the crank gear (aka starter drive gear), the needle bearing comes included within it. The inner race doesn't, but I'm replacing that too. As there was a failure and replacement of the sprag so recently, I'm attempting to eliminate everything that mechanically connects to that sprag bearing, in case there is wear or damage from previous sprag issues.

Sorry, I haven't understood your 1st point about fitting to old tracks and another sprag unnecessary? I had thought the spinning on the starter, without engaging most likely suggests a sprag fail = replace?
 

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Sorry, I haven't understood your 1st point about fitting to old tracks and another sprag unnecessary? I had thought the spinning on the starter, without engaging most likely suggests a sprag fail = replace?

I wouldn't have expected the sprag to have failed in such a short time as you said previously the sprag was replaced by the PO only about 500 miles ago (however many starts that is?).
However, going back to your first post in this thread I noticed it says "new sprag clutch and sprocket etc." so my apologies for missing that the engine sprocket also appears to have been changed as I wouldn't have expected the sprag to have failed or the engine sprocket track to have become damaged in such a short mileage.
 

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I wouldn't have expected the sprag to have failed in such a short time as you said previously the sprag was replaced by the PO only about 500 miles ago (however many starts that is?).
However, going back to your first post in this thread I noticed it says "new sprag clutch and sprocket etc." so my apologies for missing that the engine sprocket also appears to have been changed as I wouldn't have expected the sprag to have failed or the engine sprocket track) to have become damaged in such a short mileage
Got it, thanks. No, I agree, although one of the local NOC guys said he recently put an AN sprag into another Commando that refused to work and that was returned and then replaced by a Norvil sourced one, which did work fine. All the metallic dust in the primary oil suggests there is something untoward. Either previously (and I'm seeing the residue), or still ongoing. That's why I've bitten the bullet and decided to replace anything touching the sprag, plus chain. Just waiting on the parts.

I still wonder about whether the electrical side may contribute to the problem.

On the electrics, having already replaced the battery with a known good one, I will do my usual checks to rule out weak alternator performance, rather than try to work out what the manual means.
 
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Now you have been through a whole lot of different problems and solutions.
I believe I too have been through most of what you describe.
Yet again.
My experience is that the original parts are too bad.
The final solution is in my experience, a new starter motor and the new parts for CNW. (costs about the same as the original from A.N)
Vidar
 

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I still wonder about whether the electrical side may contribute to the problem.
I suppose it can't be ruled out although my Mk3's sprag has always engaged even with a discharged or failing battery that wouldn't turn the engine over down to the point where the solenoid was chattering from the lack of voltage.

On the electrics, having already replaced the battery with a known good one, I will do my usual checks to rule out weak alternator performance, rather than try to work out what the manual means.

Did you do the "Testing the DC input to battery" check in the Mk3 manual, section J3 but with the Boyer Powerbox, not rectifier and Zeners?

The manual confuses me (introducing 1ohm resistance and only 9V AC @3,000rpm, which seems low). Also, I'm neg earth/ground and no zenor diodes (Boyer Powerbox). I'm used to a 3 phase stator, testing for c.0.3 - 0.5 kOhms consistent between terminals, >20V AC at tickover, 60 to 80V AC at over 4,000rpm. Post reg/rec, c.13V DC at battery terminals, tickover and >14V, <15V DC at >4,000rpm. Any reason these tests (and figures) aren't suitable on my Commando, just as a health check?

Perhaps this recent thread at Britbike might help?
 
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