Gearbox adjuster

Information relating to the Matchless G12 or AJS Model 31 650cc twin
bob121
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Location: WEST MIDLANDS UK

Gearbox adjuster

Post by bob121 »

Hope someone can shed some light on this for me. Started pulling the bike down to address some of the niggles. Got to order a few transmission parts, while compiling the list I remembered the gearbox adjuster. The one one the bike pushes the box forward. There isn't one to adjust backwards to tension the front chain. I've gone through the parts book again and would say that that is correct. There is a slot in the rhs engine plate just behind the top bolt. So it may be possible to retro fit one.
McBob
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Re: Gearbox adjuster

Post by McBob »

What you have is correct, the reaction of driving the rear wheel will pull the g/box rear ward. When adjusting the primary chain ensure the top bolt is up against the adjuster, I tapped the box back with a soft faced hammer.
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1608
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Re: Gearbox adjuster

Post by 1608 »

The adjuster is designed to move the gearbox back and forth. Adjust primary chain tension first ( approx 3/8" at its tightest spot) then tighten gearbox fixings. Then adjust rear chain tension ( 1-1/4" at its tightest spot and preferably with somebody sitting on the bike ( off its stand ) because the rear chain tightens up a bit when the bike is sat on.
bob121
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Re: Gearbox adjuster

Post by bob121 »

Cheers. It would just be nice to have an adjuster for tensioning the chain rather than the way it needs to be done at the moment.
McBob
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Re: Gearbox adjuster

Post by McBob »

I thought the same, hopefully https://www.google.co.nz/search?q=norto ... 22#imgrc=_ works for you
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Rob Harknett
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Re: Gearbox adjuster

Post by Rob Harknett »

The tensioner does adjust the primary chain. You do need to slacken of the rear wheel and adjusters, and brake plate anchor so the rear wheel can move forward. Loosen gear box nuts and adjuster. Fit chain and tension via the adjuster, lock adjuster and tighten gearbox nuts. Reset rear chain adjustment etc.. Don't forget you had to loosen the rear brake anchor that also needs re tightening. Plus re adjust brake rod.
Mick D
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Re: Gearbox adjuster

Post by Mick D »

Hi

Or you can leave the rear wheel as is and just press down on the secondary chain lower run.

Regards Mick
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Rob Harknett
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Re: Gearbox adjuster

Post by Rob Harknett »

If fitting a new primary chain, the gearbox would need to move forward, the rear chain will also need to move forward. Any alteration to the primary chain adjustment will effect the rear chain adjustment. You would need the primary chain to be quite loose to ease fitting the primary chain split link.
bob121
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Joined: Sat Jan 14, 2017 11:48 am
Location: WEST MIDLANDS UK

Re: Gearbox adjuster

Post by bob121 »

Thank you all. But there seems to be some confusion. I know how to do the adjustment. The adjuster on this box only pushes the box forward. To tension the chain you slacken the fixings just enough and knock it back. I'd prefer to use an adjuster that pulls and pushes the box. And as new chains are being fitted, now would be a good time to fit a different adjuster if it was possible.
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Rob Harknett
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Re: Gearbox adjuster

Post by Rob Harknett »

Well the system was used from pre war into the post war years on the bikes. Simply enough to do what it needed to do. In 62 years I have never had a problem. That more than satisfies me. By changing it you would need to declare the non standard fittings to your insurance company. For all insurance there is a question. Has the vehicle been changed from its standard specification.
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