1967 Norton Atlas Gearbox

jms · Mar 24, 2025

Just getting back to my Atlas project. Fell and tore my quad ligaments right off my knee cap 3 months ago and had to have them sewn back on. It was a long Winter!
Anyway sometime ago, I partially rebuilt my gearbox. New main shaft, bearings, nuts and bolts, o rings. Finally got around to turning the rear wheel forward and tried shifting through the gears. Just doesn’t seem like the mechanism inside the outer cover is catching all four gears. I haven’t put oil in the gearbox yet. I’m assuming that I should be able to do shift it through or without oil will it just be to stiff

jms · Tuesday at 9:37 AM

Ok so I did a search here ( which I should have done first ) and it looks like the problem is not enough clearance between the pawl and the ratchet spring. The spring was tight up against the pawl

jms · Tuesday at 2:43 PM

Still won't shift. Can anyone tell me if the ratchet spring leg with the two bends goes on the bottom or does it go on top and face the bottom?

jms · Tuesday at 2:44 PM

jms said:
Still won't shift. Can anyone tell me if the ratchet spring leg with the two bends goes on the bottom or does it go on top and face the bottom?

And also does it matter what gear its's in when you fit the outer cover?

Schwany · Friday at 3:47 PM

Here's quote out of the P11 manual. Kind of disagrees with tips provided by other sources.

The spring must be fitted with the straight leg in the uppermost position as illustrated. Make sure that the legs of the spring are on each edge of the pawl to enable it to trip and engage with the rachet plate.

There are probably some AMC gearbox assembly instructions in the Old Brits section in the Technical Information sticky at the top of the Norton Commando Forum.

baz · Saturday at 4:02 AM

It's been a while since I've been inside one of those boxes
But make sure the hairpin spring isn't upside down
Make sure the clearance on the spring is good
Bearing in mind sometimes even new springs don't work because they are made inaccurately
I have seen a great detailed article on this setup so do a search for it,as said above it's probably on old Brits
Good luck with your knee,the gearbox is easier to fix than your knee

kernel65 · Saturday at 5:04 AM

Won’t shift as in locked up or your gearbox is full of neutrals?

gpzkat · 2025-03-30T19:34:47-0600

It's been a while, but I struggled with the gearbox shifting on the bench on my '66 N15CS which I am fairly sure has the same gearbox. I eventually got it right. I wasn't even sure it was right until I rode the bike. I had never rebuilt a gearbox but did the full Monty.

I remember putting the countershaft sprocket on and turning it, which enabled me to get into each gear. Not immediately, but when I finally got it, I could feel each gear 'snick' in. You can do it, just keep at it and triple-check the orientation, the spring, and the centering. Put some gear oil in there and tip it upside down and backwards etc.

I recall it was in neutral when I slapped it together. I got the correct lube at West Marine, the only place that had the right stuff. That job was one of the true puzzlers of my Norton rebuild. Keep the faith, you can get there (with help from this forum) and this guide:

https://www.nortoncolorado.org/files/AMC gearbox overhaul.pdf

jms · 2025-03-31T05:43:24-0600

Schwany said:
Here's quote out of the P11 manual. Kind of disagrees with tips provided by other sources.

The spring must be fitted with the straight leg in the uppermost position as illustrated. Make sure that the legs of the spring are on each edge of the pawl to enable it to trip and engage with the rachet plate.

There are probably some AMC gearbox assembly instructions in the Old Brits section in the Technical Information sticky at the top of the Norton Commando Forum.

Yes I read the Old Britts info on it. The problem is definitely the ratchet spring. The more I fiddle with the pawl / spring clearance the better the result. Still not great though. Order a new one and though I would start frim scratch. Lord only knows what’s been done to it over the years

jms · 2025-03-31T05:47:34-0600

kernel65 said:
Won’t shift as in locked up or your gearbox is full of neutrals?

No the gears, quandrant, etc is all free. I think the ratchet isn’t making consistent contact with the quadrant. Some false nuetrals along the way as well. Can now catch 1st, neutral, 2nd, sometimes 3rd, and never 4th

jms · 2025-03-31T05:51:01-0600

gpzkat said:
It's been a while, but I struggled with the gearbox shifting on the bench on my '66 N15CS which I am fairly sure has the same gearbox. I eventually got it right. I wasn't even sure it was right until I rode the bike. I had never rebuilt a gearbox but did the full Monty.

I remember putting the countershaft sprocket on and turning it, which enabled me to get into each gear. Not immediately, but when I finally got it, I could feel each gear 'snick' in. You can do it, just keep at it and triple-check the orientation, the spring, and the centering. Put some gear oil in there and tip it upside down and backwards etc.

I recall it was in neutral when I slapped it together. I got the correct lube at West Marine, the only place that had the right stuff. That job was one of the true puzzlers of my Norton rebuild. Keep the faith, you can get there (with help from this forum) and this guide:

https://www.nortoncolorado.org/files/AMC gearbox overhaul.pdf

Thanks for this. I’ll give it a read. Pretty sure it’s a ratchet spring issue.

marshg246 · 2025-03-31T06:53:32-0600

jms said:
No the gears, quandrant, etc is all free. I think the ratchet isn’t making consistent contact with the quadrant. Some false nuetrals along the way as well. Can now catch 1st, neutral, 2nd, sometimes 3rd, and never 4th

Sounds like you're off a tooth between the quadrant and camplate. You need to be sure all four gears and neutral are selectable before trying to fit the outer cover. A false neutral between 3rd and 4th is common but only on the bench.

You can tell which way the ratchet spring goes by seeing if it sits flat and the legs are both halfway up the pawl.

You want a very small gap between each side on the spring and pawl with the pawl centralized. The smaller, without touching, the better.

It doesn't matter what gear its in when putting the outer cover on, but I find it easier in 3rd.

If you oiled everything while assembling, you don't need it filled with oil at this point. If you put it together dry, you should redo it.

jms · 2025-03-31T07:16:00-0600

marshg246 said:
Sounds like you're off a tooth between the quadrant and camplate. You need to be sure all four gears and neutral are selectable before trying to fit the outer cover. A false neutral between 3rd and 4th is common but only on the bench.

You can tell which way the ratchet spring goes by seeing if it sits flat and the legs are both halfway up the pawl.

You want a very small gap between each side on the spring and pawl with the pawl centralized. The smaller, without touching, the better.

It doesn't matter what gear its in when putting the outer cover on, but I find it easier in 3rd.

If you oiled everything while assembling, you don't need it filled with oil at this point. If you put it together dry, you should redo it.

Good info. Thanks. Old Britts shows a photo of correct quadrant / campmate orientation in 4th gear. The quadrant arm is almost touching the top of the rectangle in the inner cover. That's where mine is so I was actually thinking that it was correct. I have a new spring coming and will start there and see what happens. I did use assembly oil but I did loosen the plunger a bit thinking that it would make the process a little easier

marshg246 · 2025-03-31T07:22:29-0600

jms said:
Good info. Thanks. Old Britts shows a photo of correct quadrant / campmate orientation in 4th gear. The quadrant arm is almost touching the top of the rectangle in the inner cover. That's where mine is so I was actually thinking that it was correct. I have a new spring coming and will start there and see what happens. I did use assembly oil but I did loosen the plunger a bit thinking that it would make the process a little easier

When almost touching the top of the rectangle, is the plunger in 4th gear? Getting all gears except 4th is very suspicious for a tooth off.

You can keep the plunger tight and change gears using the two bolts that hold the quadrant and camplate in place. That way you can feel each detent.

jms · 2025-03-31T08:07:52-0600

marshg246 said:
When almost touching the top of the rectangle, is the plunger in 4th gear? Getting all gears except 4th is very suspicious for a tooth off.

You can keep the plunger tight and change gears using the two bolts that hold the quadrant and camplate in place. That way you can feel each detent.

Yes good point on the bolts! Yes its positively clicked into forth gear

jms · 2025-03-31T08:12:23-0600

jms said:
Yes good point on the bolts! Yes its positively clicked into forth gear

The ratchet isn't putting 4th where it needs to be. I muscled the quadrant arm but it does go. Just looked at the spring again. The coil does not fit flat but when the ratchet presses up against it and flatness a bit, the straight leg is all the way at the bottom of the pawl and the dog leg is a little higher on the pawl but not halfway up. Doesn't sound good does it

marshg246 · 2025-03-31T08:13:20-0600

jms said:
Yes good point on the bolts! Yes its positively clicked into forth gear

Good, then assuming the pawl moves freely without slop, you just need to get the ratchet spring right. When new from AN, they are close but not right - they still need fiddling. Sometimes it's helpful to hold the cover as it will be when installed and watch the action keeping in mind that there's nothing to keep it in place as each selection is made.

marshg246 · 2025-03-31T08:15:41-0600

jms said:
The ratchet isn't putting 4th where it needs to be. I muscled the quadrant arm but it does go. Just looked at the spring again. The coil does not fit flat but when the ratchet presses up against it and flatness a bit, the straight leg is all the way at the bottom of the pawl and the dog leg is a little higher on the pawl but not halfway up. Doesn't sound good does it

You may have the spring upside down - the legs need to be in the center of the pawl.

Britstuff · 2025-03-31T08:39:50-0600

Further to @Marsha246's comments, have a look at the following videos. I have found them and their associated series very helpful:

jan nelder · 2025-03-31T09:24:53-0600

Britstuff said:
Further to @Marsha246's comments, have a look at the following videos. I have found them and their associated series very helpful:

the first video: near the end: setting the spring clearance: you can also attach the gear lever to double check that the pawl turns and engages for either direction of change, which should have been demonstrated, to make clear it’s function.

1967 Norton Atlas Gearbox

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