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Noisy in low gears

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Noisy in low gears

Posted by Colin Peterson at July 05. 2017

Hi,

Before I tear my transmission down, which I'm in no hurry to do, I wondered if this might ring any bells with anyone.

My MKIIA 850's transmission makes a noise in first gear that sounds a bit like, say, reeling in one of those electrical extension cables where you rotate a knob on one side. Or like rubbing a lump of metal on fairly coarse sandpaper with a circular motion, only with a deeper tone. It's quite loud, and speeds up as I accelerate, as you might expect. It seems to be louder in second gear, but starts off slower again, as though it's somehow related to the change of gear, maybe something on the layshaft. It's quieter again in third gear but otherwise behaves the same, and seems to be absent in top, although maybe it's masked by engine noise and the wind. If it *is* absent in top, maybe it's because that's a direct drive from the mainshaft to the output, if I remember correctly, meaning whatever else in the gearbox is taking a rest.

It feels as though it's been doing it a long time – I've put something over 20,000 miles on the bike since I bought it – but it's getting to the point where it's so loud it's embarrassing, not to mention rather scary. Any thoughts? TIA

Colin

Re: Noisy in low gears

Posted by richard_payne at July 05. 2017

As you say, top is 1:1 and the sleeve gear is locked to the mainshaft so there is no load on the box. It's supposed to be possible to run with all the other gears removed (see the old NOC Service Notes !)

Whining in 2nd and 3rd is usually the result of worn bushes and tooth profiles. Replacing the bushes, particularly on 2nd can bring quite a reasonable respite.

A gearbox seizure is a pretty horrible thing. I'd be inclined to strip it and at least replace all bushes and bearings.

Re: Noisy in low gears

Posted by ian_saker at July 05. 2017

I would suspect the layshaft bearing at chaincase end, their life can be quite short on a commando. Certainly worth changing if you go into the gearbox.RGM or Andover do suitable uprated bearings.

 

Re: Noisy in low gears

Posted by Colin Peterson at July 05. 2017

Thanks for the prompt response! That all makes sense, although I'd say the sound is more like grating than whining. I'm glad I remembered something about it all, i.e. the 1:1 top gear – it's about 37 years since I stripped one of these boxes! And yes, a seized gearbox would be truly ... horrible. By the way the gearbox oil is up to the mark.

Ok, so I've moved a gearbox strip-down to the top of my to-do list. While I'm here, though, neither the factory manual nor the Haynes clarifies whether the gear bushes are a sliding fit, a press fit or even need reaming – I seem to remember they're a sliding fit. Any idea?

The manuals seem very clear on what else to look out for though, and the shopping list could become quite long, although I'd hope not to need the full overhaul kit from AN. Cheers for now.

Re: Noisy in low gears

Posted by richard_payne at July 05. 2017

The sleeve gear bushes are a light press fit. The rest should just tap in and they should be pre-sized. Your shafts may be a little worn anyway.

The only bush that is a bit awkward is the layshaft bush in the kickstart. It can need reaming, dependent on the degree of interference.

Best to have a pre-heated oven and an empty house before you start :)

Re: Noisy in low gears

Posted by Colin Peterson at July 06. 2017

Good to hear about the Andover layshaft bearing, and thanks for the tips on the bushes. It was the layshaft bearing that caused me to strip one of these boxes all those years ago – I remember that I could *not* get the outer race out of the casing, but my dad, who'd trained as a fitter in the Fleet Air Arm, got it out almost before I knew it! Thankfully I remember how ...! It may take a week or three, but thanks again for the input and I shall certainly let you know how I got on. Pre-heated oven and empty house not a problem! Wink

Re: Noisy in low gears

Posted by christopher_winsby at July 06. 2017

Have a look at Old Brits Norton site. Technical Articles they cover the gearbox

Re: Noisy in low gears

Posted by Colin Peterson at July 06. 2017

That's a great tip, thanks. One question, though: is there really no fibre washer for the index plunger housing? TIA (btw, if you saw a question here before about bearings, thanks but forget it, I found the answer and I've edited that question out! Embarassed)

Re: Noisy in low gears

Posted by alan_blackhurst at July 06. 2017

Andover do a complete gearbox refurb kit

Re: Noisy in low gears

Posted by Colin Peterson at July 06. 2017

Thanks, yes, I've been looking at that, and there are only two fibre washers illustrated, presumably for the drain and level screws – I'd have thought there'd be one for the index plunger housing, or maybe a copper or ally one, like for the rocker oil feed or the dome nut on the inlet rocker cover, as the index plunger housing sits near the bottom of the box. Nor is such a washer listed in the parts book, which prompted the question. Think of the fibre washer for the banjo on the Amal carb – there isn't one listed, but one is needed, and if you ask for one you can buy one. If there isn't one for the index plunger housing, that's fine too – just want to be sure! But now I'm wondering if anyone has improvised here – seeing as oil shall always get out where it can ... Cheers.

Re: Noisy in low gears

Posted by Alan Sessions at July 07. 2017

There is no washer or O ring on pre-mk3 plunger bolts - on the mk3, the case is chamfered to take an O ring (040129) plus washer (066622) - the mk3 parts manual was never updated to reflect this.

Re: Noisy in low gears

Posted by Colin Peterson at July 07. 2017

Interesting, thanks! I did not know that. I see that Andover lists the same index plunger housing for the MKIIA and the MKIII (04.0036)– no great surprise there, but it tells me that Norton clearly thought that adding a washer, and so reducing the available length of the housing, wouldn't affect the indexing. If the MKIII case is merely chamfered, I suppose a countersink bit on a drill would allow retro-fitting this arrangement to a MKIIA case – but it would probably be simpler to identify a compressible washer of some kind that would fit. I hope to start stripping my box down over the next couple of days, so I'll soon be able to see for myself, but if anyone can suggest such a washer I'd be very grateful! Cheers.

Re: Noisy in low gears

Posted by john_holmes at July 07. 2017

Or just use a sealant on the threads such as Loctite 515 or 518, it only sets when there is no air so excess stays liquid and dissolves in oil and it works.

Re: Noisy in low gears

Posted by Colin Peterson at July 07. 2017

That's a very good point! I might order some today ...! Cheers.

Re: Noisy in low gears

Posted by christopher_winsby at July 07. 2017

I had a gearbox seize back in the 70's, I was two up at the time. The bike was relatively light and low and I am over six foot it was still hard to keep rubber side down.

Before you skimp on parts due to cost think what it will cost if the bike goes down the road.

I had no audible warning, but if I heard a strange noise from a gearbox now I would not keep riding.

Re: Noisy in low gears

Posted by Colin Peterson at July 07. 2017

No indeed – that's what I thought, since starting this thread, so I now have two boxes of parts taken off the bike and sorted in the process, one full of primary and the other with what I've removed from the gearbox so far! I've absolutely no intention of skimping on cost, but it's a warning that bears repeating. Tomorrow I'm busy, so Sunday the gearbox itself comes out, all things being equal, and we shall see what we shall see.

While I'm here, the factory manual and the Haynes both say to remove the rear wheel and the centre stand. I can see how the centre stand might prove to be in the way, but why on Earth the rear wheel ...?

Re: Noisy in low gears

Posted by david_evans at July 10. 2017

The memory of that seizure is etched into my mind Chris. It was a Triumph though ChrisSmile

Re: Noisy in low gears

Posted by Colin Peterson at July 10. 2017

My latest news on this is that I've retired from the fight to remove the gearbox from the bike. For one thing, I have to work in the street, which limits my options somewhat, and it's too damn hot – think mad dogs and Englishmen! For another, I was stymied by the gearbox adjuster, I just could not access the nut that secures it on the inside of the engine plate, short of tearing out the airbox. If I had a workshop, bench etc. I'd be fine with that, but as things are I don't have the stamina. Fingers crossed that the inner bearings are ok ...

Re: Noisy in low gears

Posted by john_holmes at July 10. 2017

I used to do all my maintenance out on the street, you can get the layshaft bearing out without removing the gearbox. You disassemble the box and remove the primary so you can remove the sleeve gear and the mainshaft. You then heat the box casting in position and when drips of water sizzle on the casting take a lump of wood and from the primary side rest one end of the wood on the outside of the layshaft housing and give it some sharp raps with a hammer, the layshaft should pop out into the gearbox, the main bearing can be pushed out from the primary side using the sleeve gear or some other pusher including wood. It was not hot when I did it as I was in UK.

Re: Noisy in low gears

Posted by Colin Peterson at July 10. 2017

That's very encouraging, thank you!

Re: Noisy in low gears

Posted by christopher_winsby at July 10. 2017

Previously david_evans wrote:

The memory of that seizure is etched into my mind Chris. It was a Triumph though ChrisSmile

I seem to remember your Norton suffered a similar fate.

Re: Noisy in low gears

Posted by Colin Peterson at July 10. 2017

Ok, all gearbox internals now removed, except that pesky outer race for the layshaft – heated housing 'til water sizzled, it didn't want to know. Maybe I wasn't rapping sharply enough? (I'm not really a rap fan ...) I was using a club hammer on a lump of wood though ... Otherwise I'll have to beg, borrow or otherwise acquire a slide hammer.

The sleeve gear and inner race of the clutch-end mainshaft bearing was covered in rust-impregnated oil, per the pic ... The bearing itself isn't rusty at all, but it's slightly rough so I'm junking it. Maybe one source of noise ...

p.s. Ahem – sorry, I'm new here ... I accidentally uploaded the pic as an attachment at the first attempt, so click on the first link (rustybearing.0.JPG) to view it in your browser – the second link downloads the pic to you! And I don't see a way to delete the attachment ... Hey ho.

Attachments

Re: Noisy in low gears

Posted by david_evans at July 10. 2017

When you replace that bearing, you could consider a sealed bearing and remove the inner seal, then some grease on the lip seal to keep that lubed.

Re: Noisy in low gears

Posted by Colin Peterson at July 10. 2017

Thanks for the tips! It's donkey's years since I bought from anyone other than Andover, Norvil or Mick Hemmings, would you recommend any source in particular for a sealed bearing?

Re: Noisy in low gears

Posted by christopher_winsby at July 11. 2017

Previously Colin Peterson wrote:

Ok, all gearbox internals now removed, except that pesky outer race for the layshaft – heated housing 'til water sizzled, it didn't want to know. Maybe I wasn't rapping sharply enough? (I'm not really a rap fan ...) I was using a club hammer on a lump of wood though ... Otherwise I'll have to beg, borrow or otherwise acquire a slide hammer.

The sleeve gear and inner race of the clutch-end mainshaft bearing was covered in rust-impregnated oil, per the pic ... The bearing itself isn't rusty at all, but it's slightly rough so I'm junking it. Maybe one source of noise ...

p.s. Ahem – sorry, I'm new here ... I accidentally uploaded the pic as an attachment at the first attempt, so click on the first link (rustybearing.0.JPG) to view it in your browser – the second link downloads the pic to you! And I don't see a way to delete the attachment ... Hey ho.

The sort of heat is in an Electric oven on full and leave t soak. So when heating with gearbox still in bike I would use too heat guns on full, nozzle's inside the case wearing gloves heat until the whole lot is hot. There is a lot of metal to heat up.

Re: Noisy in low gears

Posted by Colin Peterson at July 11. 2017

Previously christopher_winsby wrote:

Previously Colin Peterson wrote:

Ok, all gearbox internals now removed, except that pesky outer race for the layshaft – heated housing 'til water sizzled, it didn't want to know. Maybe I wasn't rapping sharply enough? (I'm not really a rap fan ...) I was using a club hammer on a lump of wood though ... Otherwise I'll have to beg, borrow or otherwise acquire a slide hammer.

The sleeve gear and inner race of the clutch-end mainshaft bearing was covered in rust-impregnated oil, per the pic ... The bearing itself isn't rusty at all, but it's slightly rough so I'm junking it. Maybe one source of noise ...

p.s. Ahem – sorry, I'm new here ... I accidentally uploaded the pic as an attachment at the first attempt, so click on the first link (rustybearing.0.JPG) to view it in your browser – the second link downloads the pic to you! And I don't see a way to delete the attachment ... Hey ho.

The sort of heat is in an Electric oven on full and leave t soak. So when heating with gearbox still in bike I would use too heat guns on full, nozzle's inside the case wearing gloves heat until the whole lot is hot. There is a lot of metal to heat up.

Thanks Christopher, that makes a lot of sense – yes, there is indeed a lot of metal to heat up! I'd been playing my blowtorch on the outside of the housing ... And I only have the one. It's meant to piddle down where I am today, but I'll report back when I've tried again, cheers!

Re: Noisy in low gears

Posted by alan_blackhurst at July 11. 2017

Try a local tool hire shop for a blind bearing extractor. I bought one off eBay when I did mine only used it the once bit of a waste of money for big kit.

Re: Noisy in low gears

Posted by Colin Peterson at July 11. 2017

That's a good idea, thanks, but all the tool hire shops I'm finding around here have nothing but builder's tools, nothing so technical.

The rain held off longer than expected (piddling down now though) so I had another go using the torch inside the box. Outer race still not interested. I have devised a cunning plan/hare-brained scheme, but I'll have to wait until the rain stops ... Tomorrow's looking ok atm.

Re: Noisy in low gears

Posted by Colin Peterson at July 12. 2017

Result just in:

DIY Slidehammer United 1–0 Outer Race Asthmatic

Attachments

Re: Noisy in low gears

Posted by david_evans at July 12. 2017

It looks like the bearing you have removed is a roller so it has been replaced before and I'm surprised if it was the source of your noise. You sometimes have to shim the end float on the layshaft with a roller bearing. You can however fit a high quality ball race in that position again a deep groove item that are more expensive than a standard item but they shouldn't need shimming. Give Mick Hemmings a ring for the correct spec

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