Lay shaft bearing fears

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Usually the layshaft issue makes itself known by a noticeable dib in the back of your calf as you head off in first. If you have an issue fix it (seriously), else it's ok!

What you do is up to you, that way you can't blame me if anything happens (because it's your own choice ;)) So, are you just looking to rebuild the gearbox just in case (based on your reading & a lot of spare time ), or do you really have a problem? Are you racing, sprinting, spirited road rider, or just pottering about (as I do!).

I believe the failure of this item is progressive, rather than catastrophic, i.e. you'll get the prod in your calf before the bearing collapses (others please jump in if I'm wrong), so you have time to decide (?). My gearbox rebuilt a couple of months ago @ 94k miles, major refurb with new gears, bushes & bearings prompted by failure of return spring (examination of gears showed wear on teeth & bronze bushes breaking up - no layshaft bearing issues). Previous rebuild was at +/-47k miles - prompted by prods from kickstart & the layshaft bearing upgraded at the time & was performing well before I got stuck in 2nd in Somerset!).

More info please....
 
L.A.B. said:
I'm not sure there ever was a change as only the 040100 (6203) layshaft bearing appears in the part lists for the AMC gearbox.
No layshaft roller seems to have been fitted as standard to any Commando even though the 06-7710 roller bearing part number is listed in the 850 Mk3 parts book.
Click to expand...

It might well have been pre AMC .
 
L.A.B. said:
But still a ball bearing I believe (A2/321).
https://andover-norton.co.uk/en/shop-details/15083

Mainshaft R/H bearing and layshaft L/H bearing according to the parts books at least as far back as '49 - '50 Model 7 Dominator.
Click to expand...

Russells could have been wrong , but they were very knowledgable and had at the time huge stocks of older parts many of which were subsequently lost in a warehouse flood . What about the WDs ?
 
1973x75 said:
I have a 750 built in November 1972. I thought the poor quality lay shaft bearing covered a certain span of the 850’s, but I occasionally see advice to change it regardless of what the year of manufacture. Do I have to live in fear while riding down the road on a 750? I’d hate to tear down an otherwise good running gearbox.
Click to expand...


Getting into this thread a bit late. The layshaft bearing in my '71 Commando failed after my ownership. The kicker was hitting the rider's leg, but he stopped before it locked up.

I installed the roller bearing in my 850 a year ago after hearing the warnings here on the forums, so the next owner (in about 25 years) will know for sure ;).

~998cc
 
On mine the PO didn't know if had been changed so I picked up a roller bearing and went in. Did it with the case in place. It wasn't difficult but heating the case to pull out the bearing took some time, at least a two beer job. Once out I discovered the Portuguese bearing had been changed for a good one... Changed it to the roller anyway and buttoned it up. While your in there go over everything, sleeve gear bearing and all the gears, bushes, O rings etc
 
Did Norton ever change the source or specs on the layshaft bearing, or were they the exact same part for all production years?
 
If it were mine I would definitely open the box and see if it had been changed
I just would not sleep not knowing!!
 
maylar said:
Did Norton ever change the source or specs on the layshaft bearing, or were they the exact same part for all production years?
Click to expand...

Source yes, no doubt influenced by cost.

The standard Commando layshaft bearing was a 6203 ball bearing, part number 040100, therefore, theoretically, all were the 'same' part if not all the same quality.

The brass cage Portuguese 6203 was a poor choice of bearing. Probably used because it was cheap (cheapest?).
 
L.A.B. said:
The brass cage Portuguese 6203 was a poor choice of bearing. Probably used because it was cheap (cheapest?).
Click to expand...

Is there any evidence that another 6203 was used from a different manufacturer?
 
jbruney said:
Stop scaring me. My old gearbox is like silk.... If you stop I promise to do it this next cool season because I don't really get winter here.
Click to expand...
They don’t always cause destruction. The tale tell is when the kickstart lever taps you in the back of your leg when accelerating. That’s how my ‘72 went and then got the roller layshaft bearing replacement.
 
They don't always cause destruction but they all have the potential. When I took mine apart the balls had exited the bearing and were in the bottom of the box, some of the balls had been split into halves but the rest of the box had no damage, must have got between the gears closest to the bearings and with the balls missing in the lower bearing the bigger than normal gap between the gears allowed the balls to pass through but be split. Hate to think what would have happened if the balls had got jammed between 2 gears.
 
kommando said:
They don't always cause destruction but they all have the potential. When I took mine apart the balls had exited the bearing and were in the bottom of the box, some of the balls had been split into halves but the rest of the box had no damage, must have got between the gears closest to the bearings and with the balls missing in the lower bearing the bigger than normal gap between the gears allowed the balls to pass through but be split. Hate to think what would have happened if the balls had got jammed between 2 gears.
Click to expand...
Mine did. With cars on my ass honking. Limped home . Terrifying experience.
 
L.A.B. said:
But still a ball bearing I believe (A2/321).
https://andover-norton.co.uk/en/shop-details/15083

Mainshaft R/H bearing and layshaft L/H bearing according to the parts books at least as far back as '49 - '50 Model 7 Dominator.
Click to expand...

John Hudson is also quoted as saying the layshaft bearing was originally a roller, so by going back further to the pre Laydown box you do find a roller bearing. B2/322

https://andover-norton.co.uk/en/shop-drawing/416/pre-laydown-gearbox-shell-internals

https://andover-norton.co.uk/en/shop-details/17267/layshaft-roller-bearing-18337-b2-322-
 
kommando said:
John Hudson is also quoted as saying the layshaft bearing was originally a roller, so by going back further to the pre Laydown box you do find a roller bearing. B2/322

https://andover-norton.co.uk/en/shop-drawing/416/pre-laydown-gearbox-shell-internals

https://andover-norton.co.uk/en/shop-details/17267/layshaft-roller-bearing-18337-b2-322-
Click to expand...

But then, AN lists the 06.7710 roller bearing upgrade for all layshafts in place of the 6203 ball bearing now just like it does for Commando.

Other sources have B2/322 as a ball bearing.
https://racingnorton.co.uk/epages/4c675e64-813f-4c0a-8926-87a680c962a0.mobile/en_GB/?ObjectPath=/Shops/4c675e64-813f-4c0a-8926-87a680c962a0/Products/"0031 B2/322"

https://www.nortonownersclub.org/node/6399
 
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