No Down Shift

Greetings and Salutations Oh Wondrous Norton Owners!

While riding my '73 750 Commando, I down shifted to third, then attempted to drop to second while navigating an intersection, nothing happened. I felt the shift lever, it was loose on the down shift, but positive on the up shift. I thought if I shifted into fourth, it may sort itself out and let me down shift. Nope.

I ended up riding the last 20 or so miles stuck in fourth gear. Fortunately I only had to come to a complete stop one time. But, we made it. Now she sits peacefully in the garage with her favorite blanket on.

I have been riding her recently on a few rides, last week completing an over 100 mile ride with absolutely no issues at all.

Two years ago, maybe longer, I did have the outer gearbox cover off so that I could polish a couple of scratches. Has been working great since then, covering at least around three thousand miles.

I know I will have to take the outer cover off to inspect the shift mechanisms contained within.

Any suggestions on what I should look for?

Thank you in advance, almighty Norton gurus,

I remain your humble servant,

Steve

Check / replace the hairpin spring

Yep, the hairpin spring likely broke. It's in the outer cover, easy to replace.
BTDT

+1. It happened to me. Take the inspection cover off and get a small inspection mirror and a light for a look see.

Note: The straight leg of the spring goes on top!

Slick

You could also check the gearlever return spring (https://andover-norton.co.uk/en/shop-drawing/208/gearbox-outer-cover-kickstart-gearshift-lever - part #10).

Mine broke leaving me stuck in 2nd gear, the outer spring was fine in my case.

Mike (Mk III ES)

From memory, I think the Norton box has two spring loaded pegs with bevelled ends, which engage with the quadrant. If a peg sticks in it's hole or the spring is weak, the gear lever cannot move the quadrant which drives the selector plate.

acotrel said:

From memory, I think the Norton box has two spring loaded pegs with bevelled ends, which engage with the quadrant. If a peg sticks in it's hole or the spring is weak, the gear lever cannot move the quadrant which drives the selector plate.

Click to expand...

Yeah, but being able to shift up and not down is a classic symptom of a broken gearshift lever return spring (aka hairpin).

acotrel said:

From memory, I think the Norton box has two spring loaded pegs with bevelled ends, which engage with the quadrant.

Click to expand...

Sounds like you are thinking of a Triumph (650/750) gearbox.

Pull the outer cover and check shift ratchet mechanism. Also see if you can click the quadrant arm up and down thru the gears to rule out a problem inside the inner cover. You may have to loosen off the Index Plunger bolt a bit to make it easier to move while you rock the rear tire back and forth. Swap out the O rings on the shifter and kickstart shafts while you're in there.

The pawl assembly is a sleeve that the ratchet plate's rod extends through. Check to see that these are moving independently. If they move together due to corrosion or junk jammed in there then shifting down becomes impossible. Ask me how I know!

L.A.B. said:

Sounds like you are thinking of a Triumph (650/750) gearbox.

Click to expand...

Strange - I cannot remember what moves the quadtrant in a Norton gearbox. It must be something similar to the Triumph. Whatever moves the quadrant is probably malfunctioning. Usually with something such as that, you can see the cause of the problem almost straight away, once you have the cover off.
Come to think of it, I remember there is a pivot which operates a lever and turns the cam plate. The comment about the possibility of a broken spring might be correct.
My problem is that if something goes wrong with my bike, I just take it apart and fix it without thinking much about it. In the extreme case, I simply re-engineer the whole deal. None of it is rocket science.

acotrel said:

Strange - I cannot remember what moves the quadtrant in a Norton gearbox. It must be something similar to the Triumph.

Click to expand...

No, it's a pawl and knuckle roller.
https://www.oldbritts.com/gearbox_info.html

acotrel said:

Whatever moves the quadrant is probably malfunctioning.

Click to expand...

As already suggested it's most likely a broken hairpin spring.

My friend had motorcycles since the 1950s. He said the first time he pulled a Japanese motor apart, he shit himself. After you have done it once, every other time is easy. And old Nortons are no different.

I now have the TTI box, so my thinking is now back in the region of selector drums. I just fix things as they come without any manuals. It drives my wife crazy and she gloats when I don't look at the manual and she has, and solves a problem. It happens with flat screen TVs etc.

Guess we all at different levels of skill and knowledge , that why I’m a happy member anyways , great place to be able to find out stuff I don’t know and how to do the fix ..... maybe it not rocket science to some ,but some days it sure is easy to stump my brain and hands ....