Jubilee ( 61 ) 3rd gear gear-set

Previously wrote:

Are you sure that the problem is with the gears and not with the shifting forks?

Hi Michaiel and thanks for the reply.

Simple answer is "No idea" and I doubt that the French owner has either.

Gearbox in in a running bike and gearbox has not been internally inspected. Suspect that the owner just assumes that it is the gear pair.

Gut feeling is that, excepting abuse, these boxes are understressed and that the gears - being straight-cut - are "In" once in.

I take it that your gut feeling is that the fork is a more likely culprit?

Good morning.

I wonder if I can return a focus to my posting? - Not being rude here!

My question relates to 3rd "Jumping Out" ( not a selection issue )and an assumption that there is a problems with the 3rd gear pair.

On the basis ( assumption which may be incorrect when relating to the Jubilee ) that internals could be from the AMC "Parts Bin" then I am trying to see if these gears ( and maybe the selection forks also ) cross-reference to other models.

Anything that may make the sourcing of components easier will be a great help.

Cheers

Good morning Tony and thanks for the reply.

I have been in contact with Andy and am awaiting a 2nd reply. He has reponded but not yet on a technical level.

The owner has confirmed that his engine number is 93867 so it has a phase 1 gearbox.

Would your observation be good for both ph1 and ph2 boxes as the selector section appears to be the main modified area? I know nowt about these machines so know nothing of the modification side ( reason for a particular change/re-design ). I am assuming that you refer only to the Cam-Plate as a weakness and exclude the selector fork assembly?

Will post Andy's reply.

Kind regards

Kim

Hi Kim,

The man to ask is Andy Sochanik Lighttwins@nortonownersclub.org

Please forward your question to him, he should be able to provide you with the numbers you need.

For what it is worth it is more likely to be wear on the shifting plate where the fork selector rollers run. The wear means that the dogs are not fully engaged, this then causes them to slip, wearing more ...

Anyway, Andy is your man.

If he does respond could you please copy the response here so we all benefit.

Thanks

Tony

Andy has kindly responded withmodificationhistory and cross-references as follows :

The very early gearbox (1959) is weaker than the 1960-1963.

In 1959, the mainshaft is stepped to accommodate the clutch.

The 'step' was seen as a weak point and was eliminated in 1960.

Another change in 1960 was for sleeve gear/4th gear.

In 1959, the sleeve gear had 'holes' in its side, to receive pegs from the side of 4th gear.

In 1960, this was changed to undercut 'dogs' on both.

In the 1959 gearbox, gears 38 & 47 (mainshaft 3rd & layshaft 2nd selector gears are identical) as well as 39 and 46 (mainshaft 2nd & layshaft 3rd idler gears).

In the 1959 gearbox, gear 38 has rounded pegs; in the 1960 gearbox, gear 38 has square-cut dogs; gear 47 has rounded pegs in both.

Gears 39 and 46 (mainshaft 2nd & layshaft 3rd idler gears) remain the same up to 1963.

The weakest point of the 1959-63 gearbox is the layshaft bush at the far end in the crankcase wall, adjacent to the gearbox sleeve-gear bearing.

The bush has a tendency to work loose & spin in the casing causing serious (if not fatal!) damage. (In 1963-on later gearboxes it was pegged in place!)

It is important to check the condition & security of this bush. Check oil-hole is lined up.

Often this bush will come out with the layshaft, or on the end of your finger if inserted.

Use a wooden dowel that is a tight fit, to see if you can dislodge it.

If little or no damage has been done, Bearing-Fit Loctite will effect a repair (make sure oil way is lined up (I use a paper-clip to test).

Parts Source = NOC Spares (or Russell Motors)

This (1959-1963) gearbox is shared with AMC (AJS & Matchless âlightweightâ singles) â also the AMC 2-stroke 250cc single (Francis Barnett, James) used these gears.

So Russell Motors could be worth a shot as well â see http://www.russellmotors.co.uk/Classic%20bikes/Downloads/files/AJS%20NORTON%20MATCHLESS.pdf