Layshaft bearing once again

Upon digging into the gearbox on my MKIII, I referenced Old Brits technical articals and came upon this statement:

You can perform limited work on your gearbox in the frame, but any serious work like replacing the lay shaft bearing,which is recommended for all pre-MK3 gearboxes, should be done on the bench.

Does this mean that the MKIII gearbox layshaft bearing is improved and doesn't need replacing?

JimNH said:

You can perform limited work on your gearbox in the frame, but any serious work like replacing the lay shaft bearing, which is recommended for all pre-MK3 gearboxes, should be done on the bench.

Does this mean that the MKIII gearbox layshaft bearing is improved and doesn't need replacing?

Click to expand...

No, as the 850 Mk3 bearing (usually a Portuguese brass cage FAG 6203) is the most faiIure-prone of them all.

The layshaft bearing can certainly be replaced easily enough without having to remove the gearbox.

http://www.doov.com/apps/nortoncompanio ... ng-upgrade

Thanks L.A.B., I'll replace it!

Jim

L.A.B. said:

JimNH said:

You can perform limited work on your gearbox in the frame, but any serious work like replacing the lay shaft bearing, which is recommended for all pre-MK3 gearboxes, should be done on the bench.

Does this mean that the MKIII gearbox layshaft bearing is improved and doesn't need replacing?

Click to expand...

No, as the 850 Mk3 bearing (usually a Portuguese brass cage FAG 6203) is the most faiIure-prone of them all.

The layshaft bearing can certainly be replaced easily enough without having to remove the gearbox.

http://www.doov.com/apps/nortoncompanio ... ng-upgrade

Click to expand...

+1 you can access everything except 4th gear sleeve with out getting into the primary

just changed my bearing using the LAB method , works a treat, thanks LAB.
My one turned out not to be the Portugese bearing but the new roller bearing is so much stronger and gives great piece of mind .

ausnorton said:

just changed my bearing using the LAB method, works a treat, thanks LAB.

Click to expand...

Good to hear that's another one done, although I certainly wouldn't claim any credit for the method, but would urge anyone who hasn't replaced the standard 6203 bearing to do this job 'sooner rather than later'.

Follow-up:

Bearing came out with the shaft quite nicely at about 200f heated with heat gun. The inside of the box looked as new; it only has 10,000 miles. The bearing was like new as well but the peace of mind is worth it. Installed a roller bearing, chilled into 200f box; two .012 shims reduced end play to .005. I'm not quite sure if the shimming is all that necessary as there's no thrust load on straight-cut gears but it really can't hurt and it should keep full contact race/roller.


Jim

Heat the whole old bearing area with heat gun. Frozen new roller outer should drop right into place , gearbox shell intact in bike. :| Shim to prevent slippings out of gear. Mileage unimportant on overstressed original layshaft bearing whether be Portuguese or earlier Brit make. A priority to any Commando.