G12 with a mystery motor

Information relating to the Matchless G12 or AJS Model 31 650cc twin
MalcW
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Location: DEVON UK

Re: G12 with a mystery motor

Post by MalcW »

g5wqian wrote: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 .
Yeah, I did. I didn't mention the tacho drive (bit posh for us Model 31 DL types!), but said to look on the LH crankcase just below the fins.

Malc
Papulski2
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Re: G12 with a mystery motor

Post by Papulski2 »

For some reason I can't get my pics any smaller. However in my first pic if you slide the image over you can see the LH crankcase. Being this engine has a tacho drive but no tachometer I don't believe it is the original engine.

I haven't been able to get back to working on the clutch problem yet but before diving into the gearbox I want to make sure the problem isn't actually the clutch itself. Thought I would clean all the plates and put it back together. Maybe cable not adjusted properly? With the clutch together and the primary chain off is there any kind of test to make sure clutch is working correctly?

A few more questions:
Can the tacho drive be removed easily? No need for it.
Does the primary cover use a gasket? there wasn't one used.

I noticed on the bottom of the primary cover there is a notch for the footrest. On my bike the footrest was slightly forward of this notch. This made it difficult to reach the one screw. Because the footrest goes over the frame on both sides I couldn't remove it. I had to remove the square rod and tap the footrest back about 1/4 inch to get to that screw. Does this make sense? Did different years have different primary cover designs?
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robcurrie
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Re: G12 with a mystery motor

Post by robcurrie »

The primary cover needs a gasket - I make my own from thick gasket paper. The footrests should mount on the outside of the frame and are adjustable to allow for big to small feet.

Rob C
JEAN-NOEL
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Re: G12 with a mystery motor

Post by JEAN-NOEL »

Yes, the tacho drive could be removed easily, but you have to replace it by these items :
022385 Distributor oïl
014247 Cap, distributor housing
023106 Washer copper distributor cap. (very important to avoid a seizure of the distributor).
And above all, do not throw away the special distributor, its housing, and the special conical washer : These are highly sought after pieces.
If you decide to keep the tacho drive, I think it is necessary to renew the oïl seal to avoid leaks. Obviously, if it is missing, you have to fit a blanking plate, with 2 short screws 2BA.
JEAN-NOEL
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Re: G12 with a mystery motor

Post by JEAN-NOEL »

Just to clarify: you can remove only the tacho gear box, and seal its housing with a blanking plate. The tacho gear box is also sought..The oïl seal for the special oïl distributor is available from AMOC PARTS : 018958.
Papulski2
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Re: G12 with a mystery motor

Post by Papulski2 »

OK...took some time off from this project. Had to wait for some parts, among other things. Started to work on it again.

Started by disassembling the clutch. Found that 2 of the friction plates were stuck to 2 of the steel plates. Had to pry them apart with a screwdriver. there was some rust buildup on them but seemed to clean off ok. Reassembling was more difficult than I thought it would be. With the clutch centre on the bike I couldn't get the sprocket over the roller cage. I ended up taking off the back plate from clutch centre, put roller on the sprocket then reassemble everything. This took several attempts as you need more than 2 hands to do this :P :P

Now I've got the clutch assembly back on the bike.

My next question is....how do you install the rubber shock absorbers? I have the tool to turn the clutch hub but they don't seem to compress enough. The instruction book says to remove compress thick rubbers and take out thin rubbers first. REVERSE this to refit rubbers. Does this mean compress thin rubbers while installing thicker ones? I've tried both ways and can't get them in.

Wondering if there was a trick to this? Maybe heat up the rubbers to soften them? Just didn't want to use too much force on them.

Thanks
mdt-son
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Re: G12 with a mystery motor

Post by mdt-son »

Yes, that's the procedure. The rubbers have probably hardened after almost 60 years. I don't know a method of softening old rubber. Hard rubber will disintegrate in the end. I suggest you replace the rubber inserts. The torgue used to install the rubber inserts shouldn't be excessive. A clean-up of the adjacent surfaces and some vaseline may help when installing them.

-Knut
Papulski2
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Re: G12 with a mystery motor

Post by Papulski2 »

I did replace the rubbers with new ones. The new ones seem harder than the old ones. Thanks for the vaseline tip, I'll give that a try
mdt-son
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Re: G12 with a mystery motor

Post by mdt-son »

You didn't comment on your gearbox problem. Is it sorted?

Why didn't the clutch centre come off the mainshaft easily?

-Knut
Papulski2
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Re: G12 with a mystery motor

Post by Papulski2 »

I'm now thinking I don't have a problem with the gearbox. Originally when bike was in gear and I engaged the clutch the rear tire wouldn't turn. After removing the clutch and discovering the stuck plates now I think that was the problem. I mean if a friction plate and a steel plate are stuck together than it would be like not even using the clutch. The sprocket and center hub would still be locked together.....does this make sense?

Once I got the puller for the clutch centre it came off pretty easy. There were some burrs on the center piece. Using a small file I cleaned them up and it went back on very nicely.
Locked