Gearbox rebuild....

Classic Norton Commando Motorcycles.

Gearbox rebuild....

Postby FastFred » Sat Jun 15, 2013 12:02 pm

Stripped gearbox in the frame last few days as although I was certain it probably had an upgraded layshaft brg I realised I was perhaps living on borrowed time as I have had it 3 years. The main reason though rather than the Russian roulette I was playing was that it has some clutch basket wobble and a lot of slack in the drive. It all looks pretty good in there, there is play in the sleeve gear bushes but the gears look fine and it has a FAG NJ203E. Here's the problem (note inner chaincase still on until I make an alternator puller):

Image
Image

Basically there was no sleeve gear oil brg seal. Should there be a boss to accept that where all the crowshit weld is? There doesn't appear to be any crack between the main and layshaft brg housings. What would you do? Live without the seal? There was a fair bit of oil in the primary (it has a belt drive and I changed the crank oil seal behind the aternator pulley a few thousand miles ago, also has a good breather)? Not sure where that's from as it fly more off the back of the final drive sprocket wouldnt it?

This is the original gbox shell which I would like to keep. Help.
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Re: Gearbox rebuild....

Postby hobot » Sat Jun 15, 2013 1:26 pm

Image

Its hard for me to tell what all is welded over but there ain't really exactly a seal anywhere just a thick washer/space filler and the bearing seal, if it has one on outside face. The worn felt seal holder happens when manual torque followed against the wimpy clutch locator circlip &/or clutch spaced too close.
Last edited by hobot on Sat Jun 15, 2013 2:13 pm, edited 1 time in total.
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Re: Gearbox rebuild....

Postby FastFred » Sat Jun 15, 2013 2:09 pm

Thanks Hobot. The pictures are misleading. All that I can see is the outer spacer (29 in picture on Oldbritts) next to the mainshaft bearing, no seal. Anyway the felt seal sits between the two thin plates outboard of the sprocket. I think I am going to have to pull the casing out and reweld a boss back on for the seal aren't I? What is the outer diameter of that seal?
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Re: Gearbox rebuild....

Postby hobot » Sat Jun 15, 2013 2:24 pm

Ugh, #29 is merely a space filler with only its tight-ish fit to act as any oil sealing. It just need to fill in for that ring piece to fit, I'd just fill with JBW and mill out avoiding distorting recovery and welding softening, goof up prone hassle. Not a big issue to try to seal oil out tranny shafts anyway as hardly any oil gets up that high, which speeds the sleeve bushes dissolving which only get oil while running in 4th for some splash drain on their edges when not spinning independently in lower gears. Drains dry at stops of course. There is no oil seal on end of sleeve bushes as there just ain't hardly any oil gets there to seal inside, most leaks down clutch rod path. Atlas shells are like half the cost of the Cdo usless notched version if it comes to replacement vs cost-efforts to fix.
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Re: Gearbox rebuild....

Postby pete.v » Sat Jun 15, 2013 2:48 pm

FastFred wrote:Thanks Hobot. The pictures are misleading. All that I can see is the outer spacer (29 in picture on Oldbritts) next to the mainshaft bearing, no seal. Anyway the felt seal sits between the two thin plates outboard of the sprocket. I think I am going to have to pull the casing out and reweld a boss back on for the seal aren't I? What is the outer diameter of that seal?


I can only assume that you are an accomplished welder and machinist. Once you get your new seal, you can machine to fit. No point in asking for dimension. You surely won't start maching without the item in hand.

You may get many suggestions here and many may be to start shopping for a shell and a primary inner.

With what I see, if you decide to keep what you have and try to make it work, you'll still be spinning the chamber of that revolver. Then again you may have the expertise to pull it off.

One more thing to check is the o.d. of the mainshaft where the sleeve gear rides. If out of spec, your clutch wobble/slop will still be there even with new bushings.
Good judgement comes from experience,
experience come from poor judgement.
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Re: Gearbox rebuild....

Postby Cheesy » Sat Jun 15, 2013 3:02 pm

Are you sure the seal isnt there? I am assuming that you mean part #9 in the diagram, it looks like someone has just smeared one of those setting gasket compounds over it to stop it leaking around the out side or to help hold it in a worn hole. I measured the ID for the seal on a spare shell and it was 55.57mm and the lip was 2.25 above the machined flat
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Re: Gearbox rebuild....

Postby FastFred » Sat Jun 15, 2013 3:09 pm

Bit confused by those answers but thanks. Yes I can weld/machine but I just wanted to know the seal dims to see the depth I may need to make a boss so i can check it will clear the gbox sprocket (rear sprocket is offset). I don't know what wall thickness the shell is in that area and assuming it is 5mm plus then I can't see why a properly bored and aligned insert wouldn't fix that with some stich welding and adequate inter-cooling as long as I check for trueness/alignment after. Are you saying that you would leave this 'as is' Hobot and change the sleeve gear bushes?
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Re: Gearbox rebuild....

Postby FastFred » Sun Jun 16, 2013 1:39 am

Does 9 seal the OD of 29 then as 29 looks like a cheap grade thick washer on RGM website, not a smooth machined OD which it would have. Or does it seal the mainshaft? Must be the former?
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Re: Gearbox rebuild....

Postby kommando » Sun Jun 16, 2013 2:23 am

I think your seal is there but hidden under some unknown bodgers compound, I have a gearbox shell with seal installed and will post a pics later so you can see to compare.
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Re: Gearbox rebuild....

Postby FastFred » Sun Jun 16, 2013 2:30 am

Panic over, thanks CheesyKommando et al. That was epoxy or summat else. Will chip off. Would you recommend renewing all bushes and brgs at this stage or be a true Yorshireman (a Scotsman stripped of his generosity) and just replace sleeve bushes, check mainshaft etc?
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Re: Gearbox rebuild....

Postby JohnTy » Sun Jun 16, 2013 3:43 am

FastFred wrote:Panic over, thanks CheesyKommando et al. That was epoxy or summat else. Will chip off. Would you recommend renewing all bushes and brgs at this stage or be a true Yorshireman (a Scotsman stripped of his generosity) and just replace sleeve bushes, check mainshaft etc?


Hi Fred
RGM and AN do an overhaul kit includes bearings, bushes, seals, springs and gaskets for £140, well worth the money and do it all in one hit. I assume yours did not sound like an old bus like mine did! and required several gears as well.
Check and inspect the kick start shaft (for cracks, mine was) and the pawl, first gear carefully.
Do it once and do it properly it is the one major part that can throw you up the road :shock:
cheers
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Re: Gearbox rebuild....

Postby FastFred » Sun Jun 16, 2013 4:46 am

Will do that JohnTy. Some of gears aren't brilliant but my old mate John Hudson put some similar back into my old commando, How much wear is too much?..Will take the clusters to lads at work tomorrow and get 2nd opinion
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Re: Gearbox rebuild....

Postby FastFred » Sun Jun 16, 2013 7:01 am

I just pulled the main brg. Loads of crap behind it and the bottom of the outer race ground away about a 1mm deep where the 4th layshaft gear had been running against it...
I can see all the epoxy from the inside but can also see lettering around the outside of the 'thing' holding the seal in. Transpires this is epoxy with the lettering stamped into it (off the mainshaft brg race) which must have happened as the muppet glued the whole thing from the outside against the in-situ main brg, nice! I suspect I don't have a boss on the outside. Am I right in thinking that mainshaft OD (2&1/2") should be stepped to receive the seal which I think is around 55.5mmdia? Will wait for a response before I hit with heat and hammer, thanks
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Re: Gearbox rebuild....

Postby JohnTy » Sun Jun 16, 2013 8:40 am

FastFred wrote:I just pulled the main brg. Loads of crap behind it and the bottom of the outer race ground away about a 1mm deep where the 4th layshaft gear had been running against it...
I can see all the epoxy from the inside but can also see lettering around the outside of the 'thing' holding the seal in. Transpires this is epoxy with the lettering stamped into it (off the mainshaft brg race) which must have happened as the muppet glued the whole thing from the outside against the in-situ main brg, nice! I suspect I don't have a boss on the outside. Am I right in thinking that mainshaft OD (2&1/2") should be stepped to receive the seal which I think is around 55.5mmdia? Will wait for a response before I hit with heat and hammer, thanks


Hi Fred
the seal runs on the spacer which is locked between the sprocket and bearing on the main shaft. you must have already taken this off. it is just plain sleeve.
The seal goes in from the outside of the case up to a shoulder, the main shaft bearing fits against the shoulder on the inside.
If you do not have a parts book, have a look on Andover Norton website for a breakdown of parts http://www.andover-norton.co.uk/ under webshop and price list.
I am sure LAB will post you a link to an online or downloadable workshop manual and parts book.
JohnT
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Re: Gearbox rebuild....

Postby JohnTy » Sun Jun 16, 2013 8:43 am

Just had another look at your picture, I think the sleeve is still in the box behind the epoxy!
From what you are saying I would guess the bearing has been turning in the outer shell and it has been epoxied in to try and seal it.
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