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Only two gears

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Hi guys, I really need your help.

I had 4 gears before removing the gearbox outer cover, on my 1962 650SS, to fit new Lock ring clutch operating body.

On replacing the outer cover I find I only have 2 gears. Yes I did make sure the quadrant assembly was in line with the top of the topmost stud. Yes with the outer cover on the bench I can lever the quadrant and obtain four gears.

Before refitting the outer cover I checked the quadrant was in its correct position AND I fitted the gear change ratchet plate assembly into the quadrant and was careful to check the spring and gear selector pawl were correctly in place while I slid the outer cover into position [several times].

On checking I only had two gears.

I hope someone can put me right before I pull the rest of my fast disappearing hair out.

 

 

 

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Sounds like you could be a tooth out on the quadrant. Been there ,done that a couple of times. Very character building !!

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I think that as you were able to obtain 4 gears by using a spanner on the Quadrant nut then I am going to put my bet on the thin Gearchange Spring either being upside down or out of position.

This spring can be a real pain, in the AMC gearbox, as in order to work correctly it must have the correct shape and just touch the floating crescent shaped selector pawl.  See attachment.

Attachments
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Thanks Philip, the spring has been detached several times and I had no idea there was a right or wrong location I don't think that is mentioned in my Haynes manual.

Is there a better manual available?.

Will try again and let you know. Thanks again Roger

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Old Britts do a good Commando gearbox but its still an AMC box, 7/8's down for the spring info.

https://www.oldbritts.com/gearbox_a.html

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I have always spent time to ensure the smallest possible clearance between pawl and spring arms, and buy a few springs from different sources to have a selection to work with. All have needed some light bending with 2 pairs of pliers.

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My advice is forget about Haynes and get a copy of the Mick Hemings video from the club! I also expect it’s the spring.

dan

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Hi guys, well I am still in trouble. I bought John Hudson's DVD from the club and played it through fitting of the inner and outer gearbox covers and as far as I can tell I have reassembled the 2 covers as John did - but without success. The upper surface of the pawl is correctly in line with the top stud.

Like John I fitted the ratchet plate assembly to the inner cover and slid the outer cover into place but I now only have one gear.

I do have a small clearance between ratchet spring and gear change pawl.

I am wondering, does the gear change pawl need to be correctly positioned while sliding on the outer cover? It seems to me the quadrant, already in the inner cover, must be correctly located but do I need to position the gear change pawl, and if so into what position?

Before I fitted the inner cover the lay shaft and main shaft detached from the gear box and dropped down but I very quickly lifted them back into position. I doubt anything else dropped out of position because I am able to select all four gears by moving the quadrant with the outer cover removed. The gearbox rotates normally by rotating the rear wheel, kick start lever and also clutch drum - so I feel the problem is not not there.

Does anyone have a magic wand?

 

 

 

 

 

 

And thanks for your attachment. I am sure the spring is in the correct way round as in your attachment. In John Hudson's DVD he seemed to hold the spring in position as he slid the outer cover in place but I wasn't successful, maybe my fingers are thicker than Johns were. 

I have even tried holding the spring in place with a length of string but ...

When I hold the spring in place I do have a small gap between pawl and spring.

I now know what frustration is like.

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Roger......The fact that you are able to select all 4 gears using the Quadrant nut strongly suggests the problem lies in the gear change / selector region. Generally this is due to an issue with the selector spring but a broken return spring would also stop some of the gears from getting selected.

The return spring is almost immediately belhind the selector spring and returns the selector pawl back to the neutral position. See attachment which shows the 2 springs from the inside looking towards the outer cover.

If this section of the gearbox has not been correctly assembled then the return spring can get wedged open by the large washer that holds it in place. Especially if the large washer has been replaced by a much thicker item. The same problem will happen if the spring is cracked or broken.

The selector spring must be exactly the right shape so that it just touches the sides of the pawl. while each leg passes through the slots of the bracket.

The second attachment shows a bundle of gearbox springs sold to me as suitable for an AMC gearbox. More than half would probably not work.

Hi Philip and other helpers, many thanks for your words.

Philip, the gearbox is still in the frame so I cannot get to the quadrant nut on the outside of the gearbox case, all I have been doing is physically moving the quadrant with a screw  driver. As I said I can get fours gears and even neutral.

When I bought the bike the force required to pull in the clutch lever was huge so I fitted the correct 7/8" clutch and brake levers. I then went through the system and noticed the clutch operating lever assembly was not in line with the cable entry hole. When I removed the outer cover there was no visible sign of gearbox oil. while there I fitted a new clutch operating lever locking ring as it had been visited by too many screwdrivers. I cannot now remember if I had 4 gears before dismantling.

Do you think something became displaced when I had to lift the lay shaft  back into position?

I will now start looking at the gear change return spring and while doing that will fit a new selector spring.

Thanks again everyone and keep watching this space.

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Roger.......you should be able to both see and access the quadrant and camplate nuts from underneath..A cranked ring spanner on the camplate nut will probably be the easiest to turn.

See photos of Commando gearbox diagram and my gearbox in frame. The 650 and Commando gearboxes share many components.

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Have you put the gear lever back on the shaft of the outer cover alone and then operated the lever. I have and if the pawl spring is not right you can see the pawl not move enough to engage with the mating teeth on the ratchet plate. 

John, yes I do have the gear lever on the shaft and the outer cover in my hand. I have a small clearance between the spring and pawl carrier assembly. When I move the lever the pawl does not quite click into mating teeth on the ratchet plate.

So I suppose I must have too much clearance. Will look into this tomorrow.

Thanks again

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Here we go again, I reduced the clearance to almost nothing but I still cannot get gears. When I push the lever downwards it feels there is insufficient movement to reach a gear, when I pull it back the lever is solid, has no movement.

I checked out the gear lever return spring but that was OK. I can rotate the thin washer above the spring. The ratchet pawl is free to move on it's shaft and moves freely against the resistance of the gear lever return spring.

I then fitted a new ratchet spring with no clearance but the situation remained the same.

Does anyone live near me in East Dorset and might be able to help?

If not can anyone recommend a workshop I could ask?

Other than that I think I will have to take the box out and have an expert look at it - and all because the clutch operating lever was not in line with the cable entry. 

 

 

 

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The most obvious nearby NOC support would be a member of the Bournemouth Branch.

Further east and you are inside Solent Branch territory.

If you have very deep pockets then north of you is Norman White.

Which part of East Dorset are you residing in?

In reply to by philip_hannam1

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Hi Philip, I live in Verwood, the nearest 'big' town is Ringwood.

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In desperation I went to Norton Colorado. Their picture numbered 63 shows the top most part of the knuckle being in line being inline with the BOTTOM of the top right hand stud WHEREAS the Haynes manual page 65 shows the knuckle in line with the TOP of the same stud. I have so far been aligning the knuckle as in the Haynes manual. 

So which is correct?

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Dave.....everything you have posted is exactly what I do. The quadrant roller /knuckle is set at near the top of the slot. Possibly for a reversed gearchange or Mk 3 Commando the settings change.

Roger has stated above that he only removed the outer cover so the quadrant and camplate should not have changed. He also mentioned the gearbox all worked fine before he removed the outer.

Logically the problem lies with the gear selector.  His description a few postings above seem to support this as he mentions being able to obtain two gear changes. This indicates a problem with the half-moon quadrant (pawl) not operating the gearchange rachet. This is generally due to the spring not being the correct shape or wrongly positioned. But........

....another possibility is the rachet pin not engaging with the hole in the quadrant knuckle roller when the outer cover is replaced. Instead, it is sitting above or below the roller and thus only pushing in one direction andthereby only allowing selection of 2 gears. This would fit in with Roger's description of limited movement of the lever in one direction and something solid in the other.      See the Mick Hemmings attachment for pictorial views of chunks mentioned.

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Good morning Dave and Philip, I said in one of my posts I removed the inner cover to replace the kick starter shaft as it had been mangled by a cowboy. I also said while removing/replacing the inner cover the lay shaft and probably the main shaft became dislodged from the gearbox case. I fairly quickly repositioned both shafts and then the inner cover. Because by physically moving the knuckle end of the quadrant I was able to select four gears and all shafts were rotating freely I assumed all was well inside the gearbox. Is this possibly where the problem is?

Should I now remove the inner cover and check the cam plate location/timing?

Whatever, I really do thank you and every one for responding to my calls for help. I wonder if my hair will grow back again when this is over.

 

 

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That's what I'd do.  It's not very difficult (unless there's lots of sealant involved!)  The lever has to be fitted properly before the cover goes on.

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Dear Roger, been there myself, many years ago.

It is possible to select all gears with quadrant one tooth out, by levering it up and down, but it won't work using normal mechanism.

Sounds like you need to experiment a little. Remove outer cover, undo fixings on inner including nut on mainshaft, holding quadrant wiggle case out a little till you can drop outer part of quadrant a tooth ( inner end goes up a tooth) then put on a couple of nuts, and add end case with a couple of screws. I think you will be put out of your misery! If it now selects all four gears you can do proper assembly job.

If you need to pull inner cover to seal it have a very good look at positions and photograph them.

Hope this suggestion helps and provides a way forward, should only take half an hour.

Regards Martin

 

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Thank you Martin, I have ordered gaskets etc from the club in preparation - so watch this space.

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Thank you Dan, yes I have just received my copy from the club.

Regards Roger

 

 

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