Transmission Bearings

CanukNortonNut · Mar 11, 2025

I use a rare earth magnet on my drain plug which I modified, to make sure any metal bits get captured. (Not that there should be any, but just in case)... So open bearings for me. I also change my oil in the GB at least once a year. As I stated before this is a 100,000 miles on GB and I am just now changing the Main shaft bearings. I changed the layshaft bearing when I first purchased the bike many years ago to the NJ203E type. I believe that it had the Portuguese peril type when I first opened up the GB.

maaseyracer · Mar 11, 2025

marshg246 said:
Were they rubber seals or metal shields?

Rubber seals. Metal seals (ZZ) will not have the same friction issue, but will have friction issues as they restrict oil flow, and they do not seal, so you have contamination issues. Open is the way to go on these.

CanukNortonNut · Mar 11, 2025

maaseyracer said:
Rubber seals. Metal seals (ZZ) will not have the same friction issue, but will have friction issues as they restrict oil flow, and they do not seal, so you have contamination issues. Open is the way to go on these.

I agree. The 04.0132 oil seal (Sleeve gear Bearing) is what seals the oil from getting out including the gaskets between the three sections of the GB. But what most often is neglected is the Gear Box Sprocket Spacer 04.0131. With time the spacer although very hard gets a groove from revolving due to road grime and this in turn acts like a grinding paste and will cause a groove on this spacer. You change the oil seal and neglect to change the spacer if there is a groove present and you have possible leaks.

Andover Norton - OIL SEAL - SLEEVE GEAR BEARING - 04.0132

OIL SEAL - SLEEVE GEAR BEARING

andover-norton.co.uk

Andover Norton - GEARBOX SPROCKET SPACER - 04.0131

GEARBOX SPROCKET SPACER

andover-norton.co.uk

my Nickle's worth 4U.

maaseyracer · Mar 11, 2025

CanukNortonNut said:
I agree. The 04.0132 oil seal (Sleeve gear Bearing) is what seals the oil from getting out including the gaskets between the three sections of the GB. But what most often is neglected is the Gear Box Sprocket Spacer 04.0131. With time the spacer although very hard gets a groove from revolving due to road grime and this in turn acts like a grinding paste and will cause a groove on this spacer. You change the oil seal and neglect to change the spacer if there is a groove present and you have possible leaks.

Andover Norton - OIL SEAL - SLEEVE GEAR BEARING - 04.0132

OIL SEAL - SLEEVE GEAR BEARING

andover-norton.co.uk

Andover Norton - GEARBOX SPROCKET SPACER - 04.0131

GEARBOX SPROCKET SPACER

andover-norton.co.uk

my Nickle's worth 4U.

To make this part work I might need a sprocket spacer with a tighter tolerance fit, or I am thinking about hunting down a thin 1.25" ID o-ring to go between the spacer and the sprocket.

maaseyracer · Mar 15, 2025

I was able to make the stock spacer work by cutting a recess into it. I set the end play to about 0.005" not sure if that is too much or too little. With the detent backed off I can shift through all the gears smoothly by hand. Things feel good, let's hope it holds up. Hopefully going back in the frame tomorrow.

Going to be a few days before the bike is back on the road after that. I need to sort out my primary chain tensioner and i want to change how my tail light is wired while I am at it. Hope to be back on it next week.

Transmission Bearings

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