Help! Gearshift Indicator shaft O-Ring is wrong size.... have you any suggestions?

The gearshift indicator shaft O-Ring that I ordered from a Norton parts supplier is the wrong size. It is supposed to be the correct one and is called a number 10 and has OD .371 inches and thickness of 0.071 . Measurements are the best I could do given it is rubber!

The number 10 does not pinch the shaft groove that it is in (shaft groove is 0.235). Instead it rotates as it is a little loose. Also, there is no resistance (ie o-ring crush) when pushing it into the pawl carrier housing. This is a recipe to leak.

I did some measurements and figure that the ideal seal that grips the shaft groove should have about 0.225 inside diameter (ie be stretched a bit) and a thickness of 0.080

I have found metric seals listed that I would like to test as below. However with shipping and minimum order size, the cost is prohibitive

Thickness Inner diameter
Ideal seal (I think) 0.080 0.225

2.0mm by 5.5mm 0.078 0.216
2.2mm by 6mm 0.086 0.236

Has anyone run into this problem or can they measure a shifter seal for me? The way I measured mine was to keep tightening the calipers by one thou, until the rubber was pinched and would not fall out of the calipers.

Meanwhile I wrapped teflon tape into the indicator shaft seal goove. This increased the groove's diameter. I then installed the number 10 and it has resistance when I push the shaft in so there is some seal crush. I hope this lasts but would like to find the right seal!

With thanks if you can help

Dennis

Have heard some gb covers being modded to take better shaft seals with proper sealing lips rather than o-rings. Believe AMR in the US offered such a mod. Recall seeing in on their website when researching the timing case mods for anti wet sumping modifications.

Here's their website page:

You can get O rings in fractional or metric sizes, in various material formulation from:

Bonded (Dowty) Seals; O rings in small lots. Oil seals

oringsusa.com/

Usually, sites such as these will include a chart of O ring dimensions to help you select one byits proper number.

Slick

I have 2 big industrial O ring kits in my workshop, imperial and metric from very small to very large O rings so I have no problems finding the right size O rings for anything, always a good investment for any workshop, also have 2 full size circlip kits, keyways, shims just to name a few different kits I have, I worked in a maintenance workshop for 31 years so built up a good collection over that time, having spares on hand comes in handy, same as nuts and bolts, flat to spring washers and 2 big collection of electrical terminals.
If you work on bikes it pays to have kits, just as important to having the right tools to do any job.

Ashley

The last gb sealing rings I bought from an AN supplier in Canada were X-ring types. Seem to seal pretty well.

If you get a kit, mark "TOP" on the box. I opened one upside down. That gave me something to do for half a winter lol

Tornado said:

Have heard some gb covers being modded to take better shaft seals with proper sealing lips rather than o-rings. Believe AMR in the US offered such a mod. Recall seeing in on their website when researching the timing case mods for anti wet sumping modifications.

Here's their website page:

Norton Gearbox Cover Seal Upgrade – Alternative Motorcycle Repair

www.amr-of-tucson.com

Click to expand...

The gear indicator O-ring is '6'...:
https://andover-norton.co.uk/en/shop-details/15079/o-ring-ratchet-spindle

L.A.B. said:

The gear indicator O-ring is '6'...:

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.

andover-norton.co.uk

https://andover-norton.co.uk/en/shop-details/15079/o-ring-ratchet-spindle

Click to expand...

Exactly, whereas several of the replies have assumed the OP is talking about item 40 on the outer cover. The seal, gear change shaft. Pays to read in detail I guess.

I got a machinist ( Bruce Chessell ? ) to bore out the outer cover and press in a proper double lipped modern seal . Years back , sold the Combat .