gearbox ratchet pawl spring

G

gjr

VIP MEMBER
Joined
Mar 5, 2010
Messages
492
Country flag
What happens when the legs of the dogleg spring are too far from the pawl ?

The problem I'm having is that randomly the bike will not shift into second. I move the lever and nothing happens. Fiddling around with it will eventually get it to shift and then it works fine.

Checking the space between the spring and the pawl I have ~0.055", quite a bit more than 0.010-0.015. Do you think that resetting the clearance will solve the problem or should I keep looking ?

Thanks
Greg
 
Yes you just got to get it right been so long since I been inside my GB when things are good I leave it alone lol.
 
gjr said:
What happens when the legs of the dogleg spring are too far from the pawl ?

The problem I'm having is that randomly the bike will not shift into second. I move the lever and nothing happens. Fiddling around with it will eventually get it to shift and then it works fine.

Checking the space between the spring and the pawl I have ~0.055", quite a bit more than 0.010-0.015. Do you think that resetting the clearance will solve the problem or should I keep looking ?

Thanks
Greg
Click to expand...

Spring pawl

My workshop manual says that there should be a minimum of 0.010 in. gap between the gearbox spring arm and the pawl. on my 72 Commando. What is the maximum gap allowed? and what happens if the gap is too small or great. I have heard several people refer to a a ratchet spring in the gear box...
www.accessnorton.com www.accessnorton.com
 
I think Old Britts show the best way to set these up. It doesn't seem right when done by their instruction, but it works when installed
 
gjr said:
What happens when the legs of the dogleg spring are too far from the pawl ?

The problem I'm having is that randomly the bike will not shift into second. I move the lever and nothing happens. Fiddling around with it will eventually get it to shift and then it works fine.

Checking the space between the spring and the pawl I have ~0.055", quite a bit more than 0.010-0.015. Do you think that resetting the clearance will solve the problem or should I keep looking ?

Thanks
Greg
Click to expand...
IMHO, you want the smallest gap you can get but there must be a gap on both sides. The point is to allow it to move to engage the rachet but too loose and it will miss as it flops like a Politian.

From Old Britts. The top picture is very wrong. The second picture doesn't show the gaps, but they are there.

gearbox ratchet pawl spring


Also, the "dogleg" matters. Put it together and be sure that the ratchet spring is centered on the selector pawl (flipper).
 
Thanks Guys. It is remarkable that Norton held on as long as they did with all the things that need to be adjusted, centered, shimmed, etc. on these bikes.
 
It is my opinion that the hairpin spring is sent out to the customer needing to be bent by the customer. I bought 4 and they all seem to be different. This is a hit or miss proposition and bending them physically and accurately is difficult. Straight out of the box they're a pig in a poke. Any body come up with the same results?
 
seattle##gs said:
It is my opinion that the hairpin spring is sent out to the customer needing to be bent by the customer. I bought 4 and they all seem to be different. This is a hit or miss proposition and bending them physically and accurately is difficult. Straight out of the box they're a pig in a poke. Any body come up with the same results?
Click to expand...
Yes, bending spring steel is hard to make things identical and there are several variables in that setup that mean that the gearboxes are not the same so some "adjustment" is required.
 
I just made two tools for this job...the first is to replace the gearbox ratchet pawl assembly...the part the hairpin spring wraps around...which makes it easy to see which leg needs bending and how much. The second is the bending tool. I have a gearbox on the bench so I spent a few hours making slight bends and then trying to shift. I probably have .020 clearance between the spring and the gear selector pawl...the horseshoe shaped thing. That seemed to work best.
 
To adjust the spring:
Hold the cover vertically, in the same position as it is on the bike.
The pawl will tilt forward and rest on the lower leg of the spring.
Move the ratchet plate through its arc and check that the pawl does not touch it at any point.
If necessary, gently bent the lower leg of the spring.
Then set the upper leg of the spring so that it just doesn't touch the pawl.
Go for a paper-thin gap.
gearbox ratchet pawl spring
 
seattle##gs said:
I just made two tools for this job...the first is to replace the gearbox ratchet pawl assembly...the part the hairpin spring wraps around...which makes it easy to see which leg needs bending and how much. The second is the bending tool. I have a gearbox on the bench so I spent a few hours making slight bends and then trying to shift. I probably have .020 clearance between the spring and the gear selector pawl...the horseshoe shaped thing. That seemed to work best.
Click to expand...
If you mean .020" on each side - that's too much. It should be very close without touching. Maybe .005" on each side. You can put the lever on, hold it like it would go on the bike, and watch while shifting up and down - of course it won't stay "in a gear" but you can see the action of the spring and pawl.
 
I got it to about .007 on each side. This works better in the box on the bench. So I bent another spring for the transmission I've been fighting for months. I pulled off the outer cover thinking it would be a quick job of just tossing in the new spring but fortunately I double checked and found a lot of clearance...meaning these two boxes were not the same. I suspect that all boxes will need custom shimming. Anyway, the problem commando improved by perhaps 85%. It will need some fine tuning to improve it beyond this point.
 
seattle##gs said:
I got it to about .007 on each side. This works better in the box on the bench. So I bent another spring for the transmission I've been fighting for months. I pulled off the outer cover thinking it would be a quick job of just tossing in the new spring but fortunately I double checked and found a lot of clearance...meaning these two boxes were not the same. I suspect that all boxes will need custom shimming. Anyway, the problem commando improved by perhaps 85%. It will need some fine tuning to improve it beyond this point.
Click to expand...
Great!
 
Seems like the pawl resting on the lower leg of the spring with a paper thin gap (Ludwig) and 0.005" on either side (Greg Marsh) are in conflict, about 100% difference.

I set the clearance to 0.008"-0.010" and couldn't select any gear reliably. I'm going to have another look at it today. Besides looking at the pawl spring I'm going to see how it changes gears moving the quadrant roller by hand. Any other things to check while I'm in there ?

And I'm really glad that I didn't put a $20 / quart gear oil in it...
 
gjr said:
Seems like the pawl resting on the lower leg of the spring with a paper thin gap (Ludwig) and 0.005" on either side (Greg Marsh) are in conflict, about 100% difference.

I set the clearance to 0.008"-0.010" and couldn't select any gear reliably. I'm going to have another look at it today. Besides looking at the pawl spring I'm going to see how it changes gears moving the quadrant roller by hand. Any other things to check while I'm in there ?

And I'm really glad that I didn't put a $20 / quart gear oil in it...
Click to expand...
No, really the same. Paper is about .004 thick so if he meant it literally, he was saying a slightly narrower than me. I like the smallest achievable gap on both sides - if that's what he meant by "paper thin" then we agree completely.

I was responding to .020 which if on both sides is WAY too big and if on one side too big. I said maybe .005". Probably should have said no more than .005" - but it's not something to measure.

Put the lever on. Set the spring. Hold it like it will go on the gearbox with you looking from the gearbox side. Watch it work. The pawl must reliably catch up or down and must be equidistant from touching at rest.
 
I think I found the problem. The pawl spring was bent wrong.
gearbox ratchet pawl spring

The old spring is on the left. A new one is on the right.

The lack of bend in the dogleg twisted the coils when the legs were installed in the stop plate. The coils got 'taller' and rubbed on the ratchet plate and the carrier. See the wear mark at 1:30.
gearbox ratchet pawl spring

The spring put enough pressure on them to pull the gear position indicator up tight against the shift lever. All that was enough to turn the ratchet plate with the shift lever so it would never select the next gear. I think.

I'll have to ride it to be sure but I could select all four gears turning the rear wheel on the center stand.
 
gjr said:
I think I found the problem. The pawl spring was bent wrong.
View attachment 105780
The old spring is on the left. A new one is on the right.

The lack of bend in the dogleg twisted the coils when the legs were installed in the stop plate. The coils got 'taller' and rubbed on the ratchet plate and the carrier. See the wear mark at 1:30.
View attachment 105796
The spring put enough pressure on them to pull the gear position indicator up tight against the shift lever. All that was enough to turn the ratchet plate with the shift lever so it would never select the next gear. I think.

I'll have to ride it to be sure but I could select all four gears turning the rear wheel on the center stand.
Click to expand...
The left one is really bad IMO. The one the right has the "legs" parallel which is good, but I'm used to the dogleg being about in the middle of the leg, not back so far. No sure if that matters on not. Also, it might be the camera angle but the new one seems heavier than the old one.

Of course, if it works and can you get each gear and neutral 100% of the time you've got it right.
 
This pawl spring thing is a minefield especially in the manufacturing process. It's hard enough to bend it correctly but as I sdaid, I have 4 of them and they are all a bit different.
 

Similar threads

The yaki
Mk3 gearbox pawl spring tolerances?
Replies
10
Views
326
CanukNortonNut
CanukNortonNut
C
  • Locked
Gear lever spring and pawl
Replies
0
Views
614
cterry66
C
N
  • Locked
Spring pawl
Replies
1
Views
1,589
L.A.B.
L.A.B.
Back
Top