gearbox stuck in 1st or neutral.

This is Commando #2 , the 71, not the one I just finished.

I am having problems with the gearbox. It doesn't want to shift into 2nd gear. This bike has what looks like a set of "norville" rear sets. I have the outer cover off, the hairpin spring has good tension, bowtie looks ok. All the parts move. On the gearbox, I am able to move the selector up and down with what seems normal resistance.

Hairball ratchet spring needs some clearance, or it won't let the pawl rock correctly to engage the ratchet plate. It is a balancing act if trying to keep the clearance at a minimum. Well, it is for me anyway.

My gearbox worked fantastic until I touched it in ways it did not want to be touched. I was not able to shift out of first a couple of days ago until I gave the spring about .015" of clearance. Now I can't get 3rd though. This all happened after installing a Commando mainshaft in a (it shall not be named) P11 AMC gearbox.

The Old Brits gearbox document covers the gearbox setup better than most. I don't have the link handy. LAB probably does.

Could also be the timing of the cam plate, or as simple as a sticky detent plunger.

Schwany said:

The Old Brits gearbox document covers the gearbox setup better than most. I don't have the link handy. LAB probably does.

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L.A.B. said:

Old Britts, Assembling the Commando gearbox

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This was invaluable for me recently , the importance of shimming out the layshaft / kickshaft to eliminate any slop using rear isolastic shims helped resolve shifting issues .

brian4.2 said:

I am having problems with the gearbox. It doesn't want to shift into 2nd gear.

Click to expand...

"...doesn't want to..."?


Do you mean with the outer cover in place when you try to select 2nd gear the lever/mechanism moves but all you feel is return spring resistance with no mechanical resistance from the ratchet engaging or after the initial play has been taken up the lever/mechanism won't move?

The first video shows the pawl often not engaging with the ratchet plate but could be because the ratchet plate is below the normal 1st gear position as it is disconnected from the knuckle roller.

The second video shows you are not rotating the gear shafts (by turning the rear wheel) as you are selecting 2nd gear.

To me, that hairpin looks 'wrong', but it may just be orientation or camera angle.
It looks as if there's too big a gap below, but then the pawl also appears to touch it when returning from moving upwards......
Can't be stressed enough there should be no touching and minimal clearance either side...

brian4.2 said:

This is Commando #2 , the 71, not the one I just finished.

I am having problems with the gearbox. It doesn't want to shift into 2nd gear. This bike has what looks like a set of "norville" rear sets. I have the outer cover off, the hairpin spring has good tension, bowtie looks ok. All the parts move. On the gearbox, I am able to move the selector up and down with what seems normal resistance.

Click to expand...

The hairpin spring needs an equal gap above and below the pawl - about 10 thou is good.

If you have had it completely apart, be aware that there is some slop in the mounting holes of the pawl spring assembly. If difficult to get the spring clearance right, you may have to play around with the location of the sheet metal mounting plate.
You should be able to see it working in the outer cover before you put it back on.
Russ

It doesn't take much to make the AMC gearbox non-functional. Everybody that has had an issue with an old Norton gearbox knows how challenging the little spring can be. I'd say frustrating, but it turns into a challenge quickly once you figure out bending the spring is non-intuitive. Can't let that little spring beat me.

I'm on my 5th try. Pulled the inner cover this time and did the shimming of the layshaft. Still need to do a test ride, but I think that may have had a lot to do with my particular issue. I had .030 of endfloat. Inner cover gasket thickness can change the layshaft endfloat a little, and I installed a thicker reusable JS Motorsports silicon fiber gasket a while back. Shifting started to get iffy right around that time. My fault for being a lazy parts changer. Not the fault of the gasket. They are a life saver, because they can be used multiple times and reseal even if slightly wet with gear oil.

As mentioned, if you are in there, check it all. Don't be a lazy parts changer like I am.

I can manipulate the quadrant while bumping the rear wheel, still seems a lot of effort but the motor is not running. The banging is me jogging the rear tire. I think I got the outer cover sorted, video shows the clearance.
I am using a Norvil rearset, just doesn't feel very positive. Should I go deeper into the gearbox or does this seem normal?

brian4.2 said:

Should I go deeper into the gearbox or does this seem normal?

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The first video looks normal enough to me although I can't tell how much force you are using but as you are working against the detent spring and plunger there should be a reasonable amount of resistance because the detent will be working to hold the camplate in position.

You might find it easier if you lever between the bottom (or top) of the inner case slot and the quadrant (with a screwdriver or similar) rather than trying to move it using a rod in the knuckle roller then you may only need one hand on the lever while the other hand turns the rear wheel.

Yeah I never use the roller to shift up n' down . A medium screwdriver should do it fine . When the knuckle roller is in place I make sure it's smeared in a heavy grease to hold it in proper position , hole to be central and outwards to accept it's mate .

Thanks all. Working perfectly now. I found running a screw into the gear indicator mounting hole allowed me to manipulate the ratchet pin to meet the knuckle.