Gearbox reassamble

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Jan 10, 2006

I've opened and closed back the gearbox over a dozen times trying to make it work after rebushing and placing new bearings in there:

I "time" the quadrant and the camplate in 4th gear. Then place back the mainshaft and its fork (I have to move the camplate a bit to fit the fork) Then I place the layshaft on it's bearing and slip third pinion with it's fork into place (have to move the camplate once again to get it into place).
At this point, the camplate is not anymore into 4th gear, and it won't move anymore...

Please, I need help!
Have a look at the Oldbritts is an excellent article supported by photos showing how to do a full strip and rebuid of the gearbox. Look under "Build or restore your own commando" then go to "Building the gearbox"

Good luck

sparkplug said:
I "time" the quadrant and the camplate in 4th gear.

After setting the quadrant/camplate position as described in the manual, check the timing of the quadrant to the camplate without the gears in position by temporarily fitting the inner cover, (you may have to select 3rd to get the cover on) and then check the camplate will index from 4th to 1st and back by levering the quadrant from the top to the bottom of its travel in the cover slot.
The quadrant should not come into contact with the inner cover at either end of the slot if the camplate timing is correct.


Move the quadrant back to the neutral position, then remove the inner cover and assemble the gear clusters with the gearbox in neutral.

The factory manual does not seem to give this information (neither does Haynes) but, the illustration 'D3' in the manual dealing with gearbox re-assembly seems to show the quadrant set at the neutral position, which is different to the D2 illustration that shows the quadrant level with the stud for initial camplate timing!

Haynes Manual

The Fig. 2.3. diagram caption in my 1990 copy of the Haynes manual (p. 60) is misleading, as it shows the camplate/quadrant set at the initial timing position (quadrant level with the stud) but infers that this is the gearbox assembly position, although the photos of the assembly sequence (p. 62-63) clearly shows the quadrant to be set at either the neutral position.

Clymer Manual

-Says move camplate from 4th to 2nd gear before fitting mainshaft 3rd with its selector fork in the assembly sequence
I would like to reinforce LAB's comment about fitting the inner cover on without the gears to make sure that the quadrant does not foul on the case when at the top or bottom of it's arc. Most of the workshop manuals I have seen tell you to line up the edge of the C-shaped operating arm with one of the studs and I have seldom found this to allow the selection of all gears.
Thank you very much for your replies!

I'll try it again tomorrow following your advice, Les. I was placing everything inside with the camplate in 4th gear!

(I was once described after an aptitude test in my youth as totally mechanically INEPT!! ~ )

With that in mind I have only ever built one gearbox and that was on the Commando ~

I set the gearbox up on the coffee table in the lounge room and sat comfortably with a beer on the side and systematically put it all back to together ~ and it still works after ten years!! :shock: :D :lol: ~ AND does not leak oil ~

The only drama I had was that I put the second gear in back to front but of course that soon announced it self as being not Kosher!!!

O~ Don't get me wrong I am not saying most of us are inept.. :eek: OR that is a piece of ~~: its not ~ but it all worked out with fore thought and step by step with a little method and madness. ~

If we don't lose the rag or spit the dummy most jobs are essentially achievable ~
Hi, guys:

Sorry if I bother too much, but I've done the gearbox over and over following the Old Britts advices, Haynes manual, and the Norton's workshop manual and replacing the gears it in neutral after checking the inner cover and quadrant position in 4th gear and all I get is that I can't move the gear shift and the bike is really hard to move as, even if the gearbox should be in neutral, pushing the bike makes the engine turn!

If this helps, everything seems to move fine until I place the layshaft fork, that's when it gets jammed (rear wheel won't turn easy)
No shims in the kickstart shaft leaves a clearance of 1,5mm more or less... This is making me crazy.

I really need help!
It's bloody hard to explain, I just slip the lot in like a cassette then pin the selectors.
The Norton Owners Club do instruction videos for gearbox and motor rebuilds and I've seen a DVD offered on Ebay. Might be a good idea to try and get hold of one of these.

OK sparkplug, don't panic, as I'm sure we can all help to sort this out.

Maybe you have one of the gears in the wrong place?

This is how Mick Hemmings demonstrates how to do it in the NOC gearbox servicing DVD.

Set the camplate & quadrant to neutral.

Fit the sleeve gear to the mainshaft and fit both parts together into the output bearing.

Fit mainshaft 3rd gear with selector fork, the selector fork groove in the gear goes to the right hand (timing) side, the fork pin fits into the camplate slot at the left side. Push a bolt in through the back of the left hand fork spindle hole in the case to temporarily hold the fork in position.

Fit layshaft 3rd gear and bush to the layshaft, with the gear dogs on the right.

Fit layshaft 4th gear to the layshaft with the flat side against layshaft 3rd gear.

Fit the layshaft with the two gears into the drive side bearing, both shafts should turn freely.

Fit layshaft 2nd gear, this time the gear selector groove goes on the left hand side and the selector fork pin should fit into the right hand slot of the camplate.

Fit the selector fork spindle and tighten.

Fit mainshaft 2nd gear with the dogs to the left side.

Fit layshaft 1st.

Fit mainshaft 1st with the wide shoulder to the right hand side against the bearing.
You're great Les.

I'll try again following step by step and see what happen.

I'll keep you informed.

Thanks a lot.
Got it! One of the new bushes was still too tight it wouldn't let the other gears turn.
Things go better when you clam down.

Thanks for the help! :wink:
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