850 Transmission What may need to be replaced??

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Mark Cigainero

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Mar 1, 2007
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I have an 850 Commando transmission 1974 that was on a bike with only 2000 miles on it. I have drained the oil out of it. The oil looks good with no visible water or metal bits. The bike was running fine when put up about 17 years ago. I have the tranny off the bike for restoration and I am wondering what if anything I should replace or be worried about. Or should I just put new fluid back in and run it. It will be a weekend rider and I am not a leadfoot anymore at 53 years old. Thanks for any advise--Mark C.
 
The transmission was probably one of the best pieces of engineering on a Norton. I'd certainly change out layshaft bearings and have a good look at the kick start pawl and gear shift return springs. None of this is expensive right now but will certainly cause you grief 200 miles away from home
 
850 Transmission

Thanks guys for the good advise. I will tear into it this weekend and order a new roller bearing for the case side lay shaft. If you have any guitar repair questions please e-mail me. That is what I have done for over 30 years. Would love to return the favor somehow---Mark C.
 
I will tear into it this weekend and order a new roller bearing for the case side lay shaft.
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Check the layshaft fit into the kickstart shaft bush. I personally will not replace the bearing on the case side without replacing the corresponding bushing in the kickstart shaft on the cover end. This is a pain in the a$$, but a large tap and corresponding bolt can crank this bushing out fairly easily.
 
850 transmission what may need to be replaced

use an upgraded layshaft BALL bearing to avoid having to shim the kickstart shaft. Just saves time and effort!
 
What is an updated "BALL" bearing for the layshaft? Do you have a picture of such a bearing? If so, please post and if not, please describe.
 
Jason and Ron have given good advice, It seems false economy to strip the box and not replace these items even though the bike had done fairly low mileage. Jason the updated bearing is a 'roller' type similar to the 'Superblend main bearings, it has better tolerance to a bit of flex and is the type supplied as standard in most rebuild kits.
 
Dave,

Ok, thanks for the decription of the "updated" ball bearing. I think we are saying the same thing when I say replace with a roller bearing. I picked up the "layshaft roller bearing" nomenclature from Rabers Parts Mart some six years ago.

Jason
 
dpmellish,

Thanks for the picture of the ball bearing, and it is indeed a ball bearing, and not a roller bearing. So, how does this ball bearing differ from the one that was originally installed in the Norton gear box?

Thanks,

Jason
 
c3 radial clearance is more stable, phenolic retainer is better suited for higher rpm (the metal cage in the original is usually what fails) shield may inhibit contamination. :wink:
 
Whether you decide on the layshaft roller or upgraded ball bearing does seem to be a matter of choice, although I know Mick Hemmings recommends the upgrade FAG 6203TB ball bearing. This is a non-shielded bearing, and I can't see any real advantage in using a shielded type, personally.
 
Agreed, But if you don't want the shield, it is easily removed. A larger advantage over the FAG bearing is the cost differential!! 8)
 
dpmellish said:
A larger advantage over the FAG bearing is the cost differential!!
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Yes, I know Ron L was quoted $132.99USD for the FAG 6203TB.P63 and I can't quite understand why that bearing is so expensive in the US? As they are only around £25-28.00GBP from Mick Hemmings or Norvil.
The bearing Mick Hemmings sold me would seem to be the standard TB type, although he apparently supplied a TB.P63 to Keith1069?
The FAG TB bearing doesn't seem to be that easy to find, however a check around the discount bearing websites turns up an equivalent NKE (Austria) TB.P63 bearing for £26.27GBP (inc. UK tax & postage). The standard 6203TB being a little cheaper. And cheaper still, if you buy 20 of them!
 
While I agree that shimming the layshaft when using the roller bearing is a good idea, it is interesting to note that Norton did not shim this bearing when they installed it, nor do they offer any shims with bearing P/N 067710. This may have been a partial cause for the self-destruction of the Mk3 Portugese roller bearing.
 
Ron L said:
While I agree that shimming the layshaft when using the roller bearing is a good idea, it is interesting to note that Norton did not shim this bearing when they installed it, nor do they offer any shims with bearing P/N 067710. This may have been a partial cause for the self-destruction of the Mk3 Portugese roller bearing.
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I know that John Hudson specifically mentions failure of the Portuguese SKF ball bearing in the NOC Service Notes, not a roller?

Many Mk3s apparently having the layshaft ball bearing fitted, as has been commented on here before.
 
Ahhhh..... The light finally goes on. All these years I thought that when Norton went to a roller in the '75 model, that was the infamous Portugese bearing. I knew that the parts book still showed the ball bearing, but I didn't understand that they changed suppliers for the ball bearing. My Mk3 box and another I did a couple years ago both already had FAG roller bearings on the layshaft when I rebuilt them.

I do know that AMC used the roller bearing in this gearbox in the pre-war years. I don't know if they recommended or supplied shims, though.

That's what I like about this list, you learn something new almost every week.
 
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