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Gearbox question

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Gearbox question

Posted by Tony Duffield at December 10. 2012

Norton AMC gearbox 1962 Dominator.

The O Rings for the Quadrant Screw and Camplate Screw are leaking, I have a Norton gearbox overhaul instruction from Mick Hemmings but I cannot determine if the O Rings can be changed without dismantling the whole gearbox.

Any suggestions?

Thanks

Tony

Re: Gearbox question

Posted by ian_allen at December 10. 2012

Hi.

The 'O' rings are just under the washers of the securing bolts on the outside of the box. As long as the box is out  of the bike (otherwise the quadrant bolt is fouled by the engine plate) it's easy to replace them. It's worth removing any marks on these washers with a bit of wet and dry on a bit of plate glass (or replacing them if they are badly marked) and smearing a dob of grease on 'O' rings' surfaces.

Regards.

Ian.

Re: Gearbox question

Posted by Tony Duffield at December 10. 2012

Ian,

Many thanks for the advice, all noted.

The gearbox is on the bench just now so changing the O Rings should not be a problem.

Many thanks

Tony

Re: Gearbox question

Posted by dominic_gomes at December 10. 2012

Ian you beat me to it by seconds. I have just had a look at an old atlas box I had in the garage to check whether it could be done.

 

cheers

 

Dominic

Re: Gearbox question

Posted by arpad_mura at May 12. 2017

Hello All,

at first, sorry for bad english. I have problem with the gearbox on my 1970 750 Commando. During winter, I did some work on it. I changed all of the bearings (small mainshaft was badly worn). I did not removed the quadrant and the camplate. But after repair, I have problem with the first and fourth gear. First is hard to shift when stayind, fourth is jumping out. So I thing, I had to move with quadrant-camplate position, even if i did not noticed. I remebmer, whet I tried to tight the quadrant screw, I moved quadrant to max top position without inner cover, so maybe, that was it. My question: am I able to set correct position with only gearbox covers removed? Or do I have to remove the primary drive and both gearbox shafts?

Thank You very much, cheers Arpad

Re: Gearbox question

Posted by Jonathan Soons at May 13. 2017

Previously arpad_mura wrote:

Hello All,

at first, sorry for bad english. I have problem with the gearbox on my 1970 750 Commando. During winter, I did some work on it. I changed all of the bearings (small mainshaft was badly worn). I did not removed the quadrant and the camplate. But after repair, I have problem with the first and fourth gear. First is hard to shift when stayind, fourth is jumping out. So I thing, I had to move with quadrant-camplate position, even if i did not noticed. I remebmer, whet I tried to tight the quadrant screw, I moved quadrant to max top position without inner cover, so maybe, that was it. My question: am I able to set correct position with only gearbox covers removed? Or do I have to remove the primary drive and both gearbox shafts?

Thank You very much, cheers Arpad

Hello Arpad.  This should be a new thread. Maybe the webmaster will take care of that.  If you just need to shift the quadrant by a tooth then you can do that by removing the outer cover, clutch throw-out mechanism, and mainshaft nut. Then you can slide the inner cover out a little and rotate the quadrant. Then replace inner cover and check the gear shifting with the outer cover off. Just work the quadrant manually. All shafts can stay in place. BUT this is only to check if it works right with this change. If it does shift ok then you have to dismantle both inner and outer covers and redo the gaskets.

Difficulty selecting first is probably unrelated. More likely clutch adjustment.

Re: Gearbox question

Posted by richard_payne at May 13. 2017

You certainly don't need to dismantle primary drive or the sleeve gear but I thought from memory that it was necessary to back off the cam plate retaining screw and move the plate inwards in order to re-index it with the quadrant. This means removing the selector fork spindle. I'm not sure if you can then jiggle it but it's probably easier to remove the pinions.

I don't know if you were using an official Norton manual but in my opinion the drawing showing quadrant position (with the inner cover removed) is rather misleading. If you set it or allow it to move that high then under dynamic conditions, the quadrant arm will contact the top of the slot in the inner cover. However, you can see if this is happening simply by removing the outer cover.

If the quadrant arm is not contacting the top of the opening in the inner cover then this is not your problem as it does indeed come fairly close when correctly set.

Re: Gearbox question

Posted by Jonathan Soons at May 13. 2017

Previously richard_payne wrote:

You certainly don't need to dismantle primary drive or the sleeve gear but I thought from memory that it was necessary to back off the cam plate retaining screw and move the plate inwards in order to re-index it with the quadrant. This means removing the selector fork spindle. I'm not sure if you can then jiggle it but it's probably easier to remove the pinions.

Right. I described that wrong. I am getting mixed up with a quadrant that pivots in the inner cover like Triumphs (and BSA but they don't index anyway, quadrant and camplate combined into one). I have built a few of those since I did a Norton. I should have gone and looked but it is raining.

Re: Gearbox question

Posted by arpad_mura at May 19. 2017

Hello bikers,

thak You for the answers. I dismantled it again and I did not found any problem in the quadrant-plate position. It was in the right position in accordance with the manual. Before repair my gearbox worked good (reminding that realy badly worn small mainshaft bearing was the reason of my repair).

Now I am thinking about two possible problems.

1. - I changed both bushing in sleeve gear. Being dismantled, it seemed that I did it well with small gap and it turned on mainshat well. Now, when inner cover was out and clutch as well with loosen clutch centre nut, mainschaft is turnig bad in sleeve gear (other is loosen or out so it must be in sleeve gear bushing) I mean it turns but it also drifts sleeve gear with secondary chain wheel. Do You thing that this could cause a problem with shifting, mainly fourth gear?

2. - Before reapir I had quite big gap between kickstart shaft and layshaft. About 2,5 mm (seriosly and it worked). So I shimmed it to 0,4 mm between inner cover and kick-shaft. I thing it is not bad, but now I really do not know what I have to thing about.

Thank You very much for opinions

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