Gearbox - able to shift up but not down

mikechelsea · Sep 14, 2016

Greeting fellow Nortonists - Has anyone had the issue below, or have any thoughts on what the problem might be?

The problem: Started my 71 Commando, couldn’t get into 1st, so rode off in 2nd. I was able to shift into 3rd and 4th, but not back down.
Took off the front cover and there was lots of surface crunk, which looked to be stopping the pawl from doing its job. There was also a very small chip in one of the teeth in the ratchet plate.

I cleaned everything, replaced both springs and ratchet plate and reassembled (following tips found here, Clymer, old Brits, and Norton Tech notes).

I could run through gears in garage, and they worked OK for a short block shifting up to 2nd, but once into 3rd, I couldn’t shift down to 2nd, but could shift up to 4th. SOL again.

I’m confident that the outer cover is sorted - there is a least a 10 thou between pawl and spring, and it DID work in the garage and shifting as far as second initially.

So, I’m heading into the inner cover…  Thoughts or suggestions? Gear issue, cam plate, shifter forks, what could cause this problem?

Many thanks in advance!

pete.v · Sep 14, 2016

mikechelsea said:
Greeting fellow Nortonists - Has anyone had the issue below, or have any thoughts on what the problem might be?

The problem: Started my 71 Commando, couldn’t get into 1st, so rode off in 2nd. I was able to shift into 3rd and 4th, but not back down.
Took off the front cover and there was lots of surface crunk, which looked to be stopping the pawl from doing its job. There was also a very small chip in one of the teeth in the ratchet plate.

I cleaned everything, replaced both springs and ratchet plate and reassembled (following tips found here, Clymer, old Brits, and Norton Tech notes).

I could run through gears in garage, and they worked OK for a short block shifting up to 2nd, but once into 3rd, I couldn’t shift down to 2nd, but could shift up to 4th. SOL again.

I’m confident that the outer cover is sorted - there is a least a 10 thou between pawl and spring, and it DID work in the garage and shifting as far as second initially.

So, I’m heading into the inner cover…  Thoughts or suggestions? Gear issue, cam plate, shifter forks, what could cause this problem?

Many thanks in advance!

Number 4 may be upside down. Flip it!
http://www.oldbritts.com/1972_g6.html

CanukNortonNut · Sep 14, 2016

pete.v said:
mikechelsea said:

Greeting fellow Nortonists - Has anyone had the issue below, or have any thoughts on what the problem might be?

The problem: Started my 71 Commando, couldn’t get into 1st, so rode off in 2nd. I was able to shift into 3rd and 4th, but not back down.
Took off the front cover and there was lots of surface crunk, which looked to be stopping the pawl from doing its job. There was also a very small chip in one of the teeth in the ratchet plate.

I cleaned everything, replaced both springs and ratchet plate and reassembled (following tips found here, Clymer, old Brits, and Norton Tech notes).

I could run through gears in garage, and they worked OK for a short block shifting up to 2nd, but once into 3rd, I couldn’t shift down to 2nd, but could shift up to 4th. SOL again.

I’m confident that the outer cover is sorted - there is a least a 10 thou between pawl and spring, and it DID work in the garage and shifting as far as second initially.

So, I’m heading into the inner cover…  Thoughts or suggestions? Gear issue, cam plate, shifter forks, what could cause this problem?

Many thanks in advance!

Click to expand...

Number 4 may be upside down. Flip it!
http://www.oldbritts.com/1972_g6.html

+1 The dogleg bend needs to be on the bottom run. Check that.
Cheers
Thomas
CNN

ashman · Sep 14, 2016

The problem should be in your outer case with the spring etc, when you are changing gears in your garge are you spinning the back wheel as you shift up or down while on the centre stand as this makes it easier to shift into the gears, have you taken it for a run after looking in the outer case, if that spring isn't set right on the pawl or up side down it will do what is happening.
Has the gear box ever been rebuilt anytime in the 45 years or unknown if it has, maybe its time for a pull down and have a good look inside might just need a good clean inside.
I had a simlar problem once mine upshifted but had troubles down shifting what caused mine was the gear lever shaft, the small shaft that goes through the gear shaft for the gear indicator was ceased up from lack of lub, knocked it out, cleaned it up and put some clean grease on the shaft and the problem was fixed, just something simple.

Ashley

Gearbox - able to shift up but not down

mikechelsea

pete.v

CanukNortonNut

ashman

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