G12 with a mystery motor

Information relating to the Matchless G12 or AJS Model 31 650cc twin
cbranni
Member
Posts: 1439
Joined: Sat Oct 09, 2010 9:17 pm
Location: ABERTAWE UK

Re: G12 with a mystery motor

Post by cbranni »

Nothing to do with the problem but are the three 1/4" dia fixing holes in the shock absorber plate correct as in they are not counter sunk to take the screw head or is the plate on the wrong way round.

Image

Colin
only dead fish go with the flow
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: G12 with a mystery motor

Post by Mick D »

cbranni wrote:is the plate on the wrong way round.
Good spot :)

The plate is on the wrong way around - hence the threaded holes in the centre not being visible through the holes.

Regards Mick
Papulski2
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Posts: 14
Joined: Sat Feb 29, 2020 4:16 pm
Location: New Jersey USA

Re: G12 with a mystery motor

Post by Papulski2 »

Thanks for the info.

Looking in the instruction book, pg 52 the plate is backwards. Don't have the screws for it and didn't find them in the spares dept. Any suggestions where to find them? Is this plate easy to remove? Can it be done while on bike?

The spares dept isn't shipping to USA right now so can't get the clutch extractor for awhile. The hub feels loose on the spline. It's almost like it gets caught on the threads on the main shaft if that makes sense. Probably just burrs like Mick said.

I'm really hoping my problem is clutch related and not the gearbox. The cable I installed was new but because the handlebar grips have the adjusters on them I had to modify them a little to make them fit. Removed about 1/2 inch from outer casing. Appears to function ok as it raises the lever in the gearbox
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: G12 with a mystery motor

Post by Mick D »

Hi

If its just a burr on the end of the shaft and there is some end float you may be able to shock it off. Pull the centre outwards while tapping the main shaft with a plastic hammer.

The plate on mine was gummed on with age - yours may be easier as its been off fairly recently. Its easier to wait until the centre is off of the shaft, then tapping the splined centre from the rear, (inside), will cause the spider to push the plate out.

The screws are nothing special, you should be able to pick them up in the States.

Regards Mick
Papulski2
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Posts: 14
Joined: Sat Feb 29, 2020 4:16 pm
Location: New Jersey USA

Re: G12 with a mystery motor

Post by Papulski2 »

Just remembered something stupid I did a few years ago that might cause my gearbox problem. Please don't yell at me :headbang:

After installing the engine I realized the spring for the center stand wasn't in place. It was a real pain between the frame and gearbox. To give me clearance I removed what I thought was the drain plug. Instead it was a plug with a spring loaded plunger. Could doing this have caused my gearbox issue?
Mick D
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Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: G12 with a mystery motor

Post by Mick D »

Papulski2 wrote:it was a plug with a spring loaded plunger. Could doing this have caused my gearbox issue?
Hi

That's the spring loaded plunger that engages with detents in the cam plate to position it correctly during gear selection, I can't imagine you could have done any damage removing and refitting it and if you can still select four gears and a neutral its not the issue.

Regards Mick
Papulski2
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Posts: 14
Joined: Sat Feb 29, 2020 4:16 pm
Location: New Jersey USA

Re: G12 with a mystery motor

Post by Papulski2 »

Only neutral, first and 2nd gear.
cbranni
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Joined: Sat Oct 09, 2010 9:17 pm
Location: ABERTAWE UK

Re: G12 with a mystery motor

Post by cbranni »

Please bare in mind you may not be able to select all gears without turning either the input or output shaft to align the dogs, between changes, just a thought.

Colin
only dead fish go with the flow
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: G12 with a mystery motor

Post by Mick D »

Papulski2 wrote:Only neutral, first and 2nd gear.
Hi

Plunger is not the issue then.

Is the clutch centre rotation locked solid or will it move slightly in either direction?

If it moves can you see the main shaft rotating a little or is all of the movement play in the splined drive?

Regards Mick
g5wqian
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Location: wiltshire
Location: near swindon wilts

Re: G12 with a mystery motor

Post by g5wqian »

not sure if someone else mentioned it before me , but the engine number , if it had one would be located just around the corner from that tacho drive , on crankcase on your left leg side just below the cylinder fins .
i think the pic you posted was showing the opposite side of crankcase .
Locked