MKIII diagnosing metal shavings in primary case

Hi all,

As I've been fine tuning the carb on my newly running Commando I've been noticing a very audible rotational noise that sounded like it was coming from the primary case. I've had 7oz ATF in there so I wasn't expecting it to be quite so loud. I opened the primary up to take a look and found fine metal shavings in the oil. It appears to largely be aluminum as it is not magnetic, though I did also find a very small amount that was magnetic.



All appeared OK at the alternator so I checked behind the clutch basket and did find a very small bevel. I also noticed as can be seen that the main shaft is fairly out of alignment with the inner cover, corresponding to where the bevel is being cut in.



I had prioritized the location of the inner cover to get the stator and rotor to align properly, as there is a tight spot at about 5 o'clock. However it appears doing so may have messed up the main shaft alignment. I did not find any other areas in the primary case that look like they are obviously rubbing. So I guess my question is how important is it to align both the main shaft and the alternator when assembling the primary? Are there strategies to do both simultaneously? I've seen custom spacers cut for the main shaft alignment but I don't have access to the tools to build such a thing.

One thing I will note is I removed a shim washer behind the clutch basket on my rebuild because doing so seemed to improve the alignment of the chain. This had the added benefit of allowing enough space to use an o-ring nut at the end of the main shaft. I have already had to shave the original nut down to .331" to get the o-ring nut to fully seat, and fear taking it down any further, so simply putting the shim back in would be tough.

As a final thought I did notice the retainer ring on the clutch center allows the clutch basket some degree of play (see gap in pic). Does anyone ever shim this to get that tighter or is it a little loose by design? Tightening that up could potentially help prevent the beveling...?



Sorry for the scatter shot thoughts/questions here, but in a nutshell any help to diagnose the metal shavings and address how to stop it from happening would be greatly appreciated.

Thanks,
Anthony

A closer inspection of the chain itself has revealed this:

Assuming this is new wear, any ideas what might be causing it? Its only on the one side. I'm a bit stumped.

Anthony

Mk3 + ATF = Not Recommended :-(

EstuaryBoy said:

Mk3 + ATF = Not Recommended :-(

Click to expand...

Oh no kidding? Why and what should be used instead?

The ATF is too thin for the chain tensioner so you get a loose chain, 20/50W is recommended instead.

I just did a little research on this, I’ll try 20w50 when I put it back together. Is that expected to resolve most of this or are there other things to consider while I have everything apart?

If that is the outside of the chain , i suggest that you look at the back side of the plate cover for the chain tensioner . Make sure it is flat . On mine I found the rivets rubbing on the back side .

Are you saying your clutch hub is loose in the bearing? That should be a light press fit.

Also, make sure you have a gasket between the chain tensioner aluminum body and the sheet steel plate. This is not shown in the parts catalog or mentioned in the manual [unless you had my edited version]. The gasket was added later, as a service bulletin. See

https://andover-norton.co.uk/en/shop-details/16850/gasket-p-chain-tensioner-body

chaztuna said:

Also, make sure you have a gasket between the chain tensioner aluminum body and the sheet steel plate. This is not shown in the parts catalog or mentioned in the manual [unless you had my edited version]. The gasket was added later, as a service bulletin. See

https://andover-norton.co.uk/en/shop-details/16850/gasket-p-chain-tensioner-body

Click to expand...

After 24 years, i only learned about that gasket this past winter thanks to it being mentioned here .. I also learned that a bend in the plate leaves a significant gap even with the gasket which allows the oil to pass right through and not being held captive as intended ..

Cheers

When I had the same, my top chain tensioner had seized fully in, so the chain was able to skim material off the bottom of the inner case. The wear was easy to see though. I had to lightly wet and dry the upper hydraulic piston, until I got a smooth action. It was possibly caused by two things:
- The top hat spacers inside both tensioner plungers, were in the wrong way round;
- The top hat spacer in the top tensioner was not the std part, longer and heavier.

Plenty of the alloy particles had made their way into my sprag bearing. Worth thoroughly cleaning that out.

Anvill said:

Hi all,

As I've been fine tuning the carb on my newly running Commando I've been noticing a very audible rotational noise that sounded like it was coming from the primary case. I've had 7oz ATF in there so I wasn't expecting it to be quite so loud. I opened the primary up to take a look and found fine metal shavings in the oil. It appears to largely be aluminum as it is not magnetic, though I did also find a very small amount that was magnetic.

All appeared OK at the alternator so I checked behind the clutch basket and did find a very small bevel. I also noticed as can be seen that the main shaft is fairly out of alignment with the inner cover, corresponding to where the bevel is being cut in.

I had prioritized the location of the inner cover to get the stator and rotor to align properly, as there is a tight spot at about 5 o'clock. However it appears doing so may have messed up the main shaft alignment. I did not find any other areas in the primary case that look like they are obviously rubbing. So I guess my question is how important is it to align both the main shaft and the alternator when assembling the primary? Are there strategies to do both simultaneously? I've seen custom spacers cut for the main shaft alignment but I don't have access to the tools to build such a thing.

One thing I will note is I removed a shim washer behind the clutch basket on my rebuild because doing so seemed to improve the alignment of the chain. This had the added benefit of allowing enough space to use an o-ring nut at the end of the main shaft. I have already had to shave the original nut down to .331" to get the o-ring nut to fully seat, and fear taking it down any further, so simply putting the shim back in would be tough.

As a final thought I did notice the retainer ring on the clutch center allows the clutch basket some degree of play (see gap in pic). Does anyone ever shim this to get that tighter or is it a little loose by design? Tightening that up could potentially help prevent the beveling...?

Sorry for the scatter shot thoughts/questions here, but in a nutshell any help to diagnose the metal shavings and address how to stop it from happening would be greatly appreciated.

Thanks,
Anthony

Click to expand...

in pic #2 the countershaft seal which is pressed into the back side of the internal primary should be reasonably concentric with the countershaft sealing collar, not as it appears. The pic suggests a short seal lifespan due to the eccentricity. The gearbox can be moved around on the bolts before tightening to minimize eccentricity. Not ideal, it is a peculiarity of the mk111.

Mart UK said:

When I had the same, my top chain tensioner had seized fully in, so the chain was able to skim material off the bottom of the inner case. The wear was easy to see though. I had to lightly wet and dry the upper hydraulic piston, until I got a smooth action. It was possibly caused by two things:
- The top hat spacers inside both tensioner plungers, were in the wrong way round;
- The top hat spacer in the top tensioner was not the std part, longer and heavier.

Plenty of the alloy particles had made their way into my sprag bearing. Worth thoroughly cleaning that out.

Click to expand...

I would replace the bearing.It is relativly easy to get rid of the finer debris but the larger chunk will still be wedged in there somwhere I think Cherrs Ian

The primary chain will be impacting the thrust washer (06.5652) that sits on the overload device. I machine a concave edge on this so the chain just clears it. Look for a shine edge on the the thrust washer. Also try and improve the siting of the gearbox in it's cradle and the cradle to engine.
Use long 10mm bolts or studs (that the plain shank is long enough to sit through both sides of the cradle)
Custom made gearbox mounting bolts/studs machined to close the clearances will also help to keep the gearbox in place.

Mart UK said:

When I had the same, my top chain tensioner had seized fully in, so the chain was able to skim material off the bottom of the inner case. The wear was easy to see though. I had to lightly wet and dry the upper hydraulic piston, until I got a smooth action. It was possibly caused by two things:
- The top hat spacers inside both tensioner plungers, were in the wrong way round;
- The top hat spacer in the top tensioner was not the std part, longer and heavier.

Plenty of the alloy particles had made their way into my sprag bearing. Worth thoroughly cleaning that out.

Click to expand...

For the chain to contact the bottom of the chaincase tells you the chain is knackered. In operation when the engine is running the top chain run will be straight (the hydraulic tensioner takes the slack on the bottom run) and when the engine load is reversed (gear changing etc) the bottom is tight and that is how the hydraulic tensioner gets the movement to operate.