Metal Flakes in the gearbox oil?

MCP · Jun 24, 2024

1974 MK2a 850 with 23,000 original miles. I noticed the shifting wasn't crisp per usual so I drained and filtered the gear box oil and found some small metal flakes. I replaced it, ran it through the gears while it was on the center stand and filtered and dumped that. I did that several times and then took it for short rides, repeating the flush.

At this point, it shifts almost good as new, with the exception of going from 1st to 2nd when sometimes I need to give it an extra push.

I'm using Belray oil at the moment.

On the last oil change I got a small sliver of metal out, 1/4" long and thin, but very little in the way of metal flakes.

The only thing I did this past winter to the gear box was replace the seals in the outer cover for the kick starter and shifter. The inner box has never been opened, and the bike was not abused. It was working great for the first 300 or so miles this season and then the shifting issue started. My plan is to pull the outer cover this week and have a look for something obvious, but what else should I be looking at?

Suggestions?

Thanks

CanukNortonNut · Jun 24, 2024

You might be looking at going deeper into the gears and shafts themselves. So open the inner cover for an exploratory. Whitworth tools are needed here.
You have replaced or know that the layshaft bearing was replaced??? A superblend type. If it has Portuguese on it, it needs to come out. too many threads on that bearing alone.
Check your Kick start pawl to see the condition as a known metal breakage point. When you say metal you are not refereeing to brass or bronze particles? You will need to take the clutch basket off... so not a simple 2 hour job.

MCP · Jun 24, 2024

CanukNortonNut said:
You might be looking at going deeper into the gears and shafts themselves. So open the inner cover for an exploratory. Whitworth tools are needed here.
You have replaced or know that the layshaft bearing was replaced??? A superblend type. If it has Portuguese on it, it needs to come out. too many threads on that bearing alone.
Check your Kick start pawl to see the condition as a known metal breakage point. When you say metal you are not refereeing to brass or bronze particles? You will need to take the clutch basket off... so not a simple 2 hour job.

The layshaft bearing is original. I've seen both brass and silver flakes. When you refer to the clutch basket, is that what Andover calls the Clutch Chainwheel on the primary side? Thanks

Tornado · Jun 24, 2024

MCP said:
The layshaft bearing is original. I've seen both brass and silver flakes. When you refer to the clutch basket, is that what Andover calls the Clutch Chainwheel on the primary side? Thanks

You need to get everything off tge gb main shaft, as final drive sprocket has to come off to pull the main shaft out of gb.

Ive done a complete gb rebuild without removal from frame. Followed the Mick Hemmings DVD from the INOC. Ĺlayshaft bearjng on my 74 850 wascthe notorious Portuguese P.O.S., but it was not broken at arojnd tge 10k miles mark. Replaced it as preventative with the Hemming recommended phenolic cage ball bearing. Did all bushings, bearings, seals and gaskets, plus KS pawl, springs and clutch arm parts which were fairly badly worn.

CanukNortonNut · Jun 24, 2024

MCP said:
The layshaft bearing is original. I've seen both brass and silver flakes. When you refer to the clutch basket, is that what Andover calls the Clutch Chainwheel on the primary side? Thanks

On the primary side you need to remove the outer cover and drain the oil. You will need a special tool to remove the clutch spring plate centre to get at the nut and then remove the Clutch sprocket 062482. Or clutch complete 062481, This is what you will remove as a whole. Follow the Shop manual. Use the Parts manual or go to Andover Norton Website for a good break down on parts for your year Commando. If the layshaft bearing is original then "they will fail". They have a bronze cage that falls apart and then dumps the ball bearings into the gear cluster where they should not be and create havoc to your detriment. Better bearings are available from your local British Cycle Supply or Walridge Mortors.
Check the Technical Information section and go to Old Brits for gearbox repair.
Read up what you can before going in.
https://andover-norton.co.uk/en/shop-details-2/16993/gearbox-overhaul-kit-amc-1962-onward-23-items-
If you go in this deep then this kit would be a good option.

nortonmargie · Jun 24, 2024

Bonneville in the US has (relatively) inexpensive Whitworth sockets and wrenches: https://www.thebonnevilleshop.com/shop/. Suggest you tear your bike down now to avoid a lot of expense in the future. If pieces of metal are coming off, something is about to go BANG.

CanukNortonNut · Jun 24, 2024

MCP where are you located?

Fast Eddie · Jun 24, 2024

That original lay shaft bearing can lock up the drive and have you off when it fails. With a warning like this you have no choice but to stop riding, open it up and dig in.

I’m not saying it IS that for sure, but the risk, and potential consequence, of failure is way too high to ignore.

cjandme · Jun 25, 2024

I Like metal Flakes but in the Paint Job not in the gear box

Sorry 'bout that couldn't resist. But seriously maybe this is a blessing in disguise because of the layshaft bearing issue like Fast Eddie above mentioned. Cj

dobba99 · Jun 25, 2024

This 'small sliver of metal out, 1/4" long and thin' sounds like it has come off one of the gears. The basic design of the g/box years ago was never meant to transmit the power of an 850 lump, it is remarkable that it copes so well. That said this looks like one or more of the gear teeth are starting to break up. I have various gears that show this wear that has happened. Infrequent oil changes in the past doesn't help matters. You can remove most of the gearset and the layshaft bearing as well without having to dissemble the primary drive. The mainshaft and sleeve gear will be left in the box, use a mirror to check the sleeve gears teeth, if that is the one wearing out, its a primary drive off and full box strip then.

kommando · Jun 25, 2024

If the layshaft bearing is giving up the ghost then first its brass cage starts to break up and then followed by the balls escaping. The escaping balls can then get between the gears, either jamming up the gearbox or being mashed into small pieces.

concours · Jun 25, 2024

MCP said:
1974 MK2a 850 with 23,000 original miles. I noticed the shifting wasn't crisp per usual so I drained and filtered the gear box oil and found some small metal flakes. I replaced it, ran it through the gears while it was on the center stand and filtered and dumped that. I did that several times and then took it for short rides, repeating the flush.

At this point, it shifts almost good as new, with the exception of going from 1st to 2nd when sometimes I need to give it an extra push.

I'm using Belray oil at the moment.

On the last oil change I got a small sliver of metal out, 1/4" long and thin, but very little in the way of metal flakes.

The only thing I did this past winter to the gear box was replace the seals in the outer cover for the kick starter and shifter. The inner box has never been opened, and the bike was not abused. It was working great for the first 300 or so miles this season and then the shifting issue started. My plan is to pull the outer cover this week and have a look for something obvious, but what else should I be looking at?

Suggestions?

Thanks

Rebuild the transmission.

marshg246 · Jun 25, 2024

To summarize what most are eluding to, don't ride the bike - it sounds unsafe at any speed. Either fix the gearbox or have it fixed. Just removing the inner cover won't let you see much.

Any metal bigger than dust in the gearbox oil means you are on borrowed time IMHO.

dobba99 · Jun 25, 2024

marshg246 said:
To summarize what most are eluding to, don't ride the bike - it sounds unsafe at any speed. Either fix the gearbox or have it fixed. Just removing the inner cover won't let you see much.

Any metal bigger than dust in the gearbox oil means you are on borrowed time IMHO.

Surely you meant to say outer cover. Removing the inner cover will allow you to remove the selector rod, layshaft and gearset.

MCP · Jun 25, 2024

I was hoping to put this off to the fall, but considering the risks, I'll deal with it now. Thanks for all for the input.

Tornado said:
You need to get everything off tge gb main shaft, as final drive sprocket has to come off to pull the main shaft out of gb.

Ive done a complete gb rebuild without removal from frame. Followed the Mick Hemmings DVD from the INOC. Ĺlayshaft bearjng on my 74 850 wascthe notorious Portuguese P.O.S., but it was not broken at arojnd tge 10k miles mark. Replaced it as preventative with the Hemming recommended phenolic cage ball bearing. Did all bushings, bearings, seals and gaskets, plus KS pawl, springs and clutch arm parts which were fairly badly worn.

Do you know where I can get the MH video?

nortonmargie said:
Bonneville in the US has (relatively) inexpensive Whitworth sockets and wrenches: https://www.thebonnevilleshop.com/shop/. Suggest you tear your bike down now to avoid a lot of expense in the future. If pieces of metal are coming off, something is about to go BANG.

Thanks, I have some Whitworth bits but I'll see what I'm missing.

CanukNortonNut said:
MCP where are you located?

Ladysmith/Nanaimo - thanks for the info too

Tornado · Jun 25, 2024

MCP said:
I was hoping to put this off to the fall, but considering the risks, I'll deal with it now. Thanks for all for the input.

Do you know where I can get the MH video?

Thanks, I have some Whitworth bits but I'll see what I'm missing.

Ladysmith/Nanaimo - thanks for the info too

The Hemmings DVD is available to order from the Norton Owners Club in the UK. I can lend you my copy if you want, I'm in Vancouver.

Alternatively, this YouTube channel as pretty good rebuild detail for the mk3 but this is nearly identical to mk2 save for the gear selector cross shaft:
(Owner forgot to put this up as shareable on other sites, so just use the Watch on YouTube link to see it)

I am planning to help a local owner in a week or so do a partial gb rebuild, as the kicker is not engaging at all. He is in North Van, perhaps if you are able to come out you can join us...

Grandad · Jun 25, 2024

Just for general interests sake ..... it is always worth a dry run assembling the empty castings together before getting into the actual build to make sure all goes together well, easily and without a snag and then you can also see how the castings meet ( hopefully without any warping or damage that could piss oil ), same with engine cases. Any issues are then easy to sort without stripping back out gears shafts and bearings.

marshg246 · Jun 25, 2024

dobba99 said:
Surely you meant to say outer cover. Removing the inner cover will allow you to remove the selector rod, layshaft and gearset.

No, I didn't. He said he would remove the inner cover and look. I said: "Just removing the inner cover won't let you see much." I make typos and sometimes my sentence structure is not great, but in this case, it's about your reading, not my writing

Notice the first word in my sentence.

Also, stripping everything possible with the mainshaft still in the clutch means that you cannot fully inspect. For instance, you cannot see the sleeve bear bearing at all and unless you remove the rear chain, you cannot even feel that bearing's smoothness. Considering that it's likely still an open bearing and there's metal in the oil, it is certainly suspect.

Tornado · Jun 25, 2024

marshg246 said:
No, I didn't. He said he would remove the inner cover and look. I said: "Just removing the inner cover won't let you see much." I make typos and sometimes my sentence structure is not great, but in this case, it's about your reading, not my writing Notice the first word in my sentence.

Also, stripping everything possible with the mainshaft still in the clutch means that you cannot fully inspect. For instance, you cannot see the sleeve bear bearing at all and unless you remove the rear chain, you cannot even feel that bearing's smoothness. Considering that it's likely still an open bearing and there's metal in the oil, it is certainly suspect.

Been a few yrs since doing my gb, but seem to recall i could not pull layshaft out without first removing mainshaft's gear, which meant mainshaft had to come out?

dobba99 · Jun 25, 2024

marshg246 said:
No, I didn't. He said he would remove the inner cover and look. I said: "Just removing the inner cover won't let you see much." I make typos and sometimes my sentence structure is not great, but in this case, it's about your reading, not my writing Notice the first word in my sentence.

Also, stripping everything possible with the mainshaft still in the clutch means that you cannot fully inspect. For instance, you cannot see the sleeve bear bearing at all and unless you remove the rear chain, you cannot even feel that bearing's smoothness. Considering that it's likely still an open bearing and there's metal in the oil, it is certainly suspect.

Actually the OP said he would 'pull the outer cover and have a look' So not only is there miss reading of the OP post but also typos, Granted we can all make mistakes and i've dropped some beauties in the past but to claim it is my reading and not your writing is a load of cobblers.
(That is not a typo)
Note to all. Before clicking the post reply button, step away from the keyboard for a few moments, return and proof read your reply. I try to do this on each and every occasion. Many times i have corrected spelling and/or grammar or deleted what i had just typed as i realised it wouldn't be doing any good, or be seen as moaning/bitching for no good reason or to score points off someone.
Years ago at work not following this mantra landed me in hot water. Battering the keyboard and sending an email at work in the heat of the moment was not a good idea! Thank goodness for the editing function on this site...

Metal Flakes in the gearbox oil?

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