G80 front sprocket

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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crawsue
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G80 front sprocket

Post by crawsue »

In response to an earlier thread, "Biscuit" suggested that my newly purchased G80 was probably fitted with a 19 tooth front sprocket.Having made some other enquiries (from the previous owner) it would appear that he is correct.The workshop manual that I have suggests that 19 tooth is for combination use, but shows either 21 tooth or 22 tooth for general touring work. Does anyone have any information regarding what would be best? I suppose that a 500 should have enough "poke" on modern petrol to pull 22 teeth.Regards, Crawford
Hard work never killed anyone.....but why take the risk?
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Chazzyb
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G80 front sprocket

Post by Chazzyb »

I think 500cc singles with Burman boxes usually had 21 teeth, and for AMC, 22. I'm not sure you'll find a 22 tooth front sprocket for a Burman box - one with a dynamo drive at least. People who have fitted larger gearbox sprockets usually complain that first is then too high for town work or top too high for sustained highway speeds. Maybe AMC got something right then?
Charles
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Biscuit
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G80 front sprocket

Post by Biscuit »

Naughty Chazzyb, leaving red herrings. The Burman box and dynamo sprockets have nothing to do with Crawford's bike.

The spares book states 22T for G80S. When you do the job, take care you don't lose the alternator rotor key, and watch for the two spacers one either side of the sprocket. Don't remove the chain until the rotor nut is slackened. The fun starts when you replace the chain, of course it won't fit, so the gearbox has to be moved forward, this means the rear wheel has to be moved forward, if you are really out of luck you may have to increase the length of one or both chains.

Don't sell yourself short, a numpty can do it.



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crawsue
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G80 front sprocket

Post by crawsue »

Thanks ,both for your quick responses.On further detective work I find that there is a legitimate 23 tooth sprocket available for the alternator G80. Is this worth considering? Was it an AMC option? What would be the circumstances for its'fitting?Cheers,C.
Hard work never killed anyone.....but why take the risk?
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Chazzyb
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G80 front sprocket

Post by Chazzyb »

quote:
Naughty Chazzyb, leaving red herrings. The Burman box and dynamo sprockets have nothing to do with Crawford's bike.


Naughty, why? I haven't the first idea about his bike apart from being a G80S! Unless I'm mistaken, some G80Ses have Burman boxes and dynamos.
Charles
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Biscuit
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G80 front sprocket

Post by Biscuit »

Crawford initially said it was a 1959/61 G80S, as does his bio.



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TommoT
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G80 front sprocket

Post by TommoT »

...as an aside to this discussion, I can tell that on my dynamo/burman G80, I left the 21 tooth engine sprocket alone and played with different gearbox sprockets instead. They were/are more readily available. Standard gearbox is 16T. I found an 18T and tested it. Clearly too much for the G80 engine to handle. First gear too tall, uphill or headwind cruise speed was impaired. Last year 17T sprockets became available, and it does the trick for me. Acceleration and take-off still acceptable, ordinary out of town cruise speed raised by approx. 6mph, or an equivalent reduction of rpms at previouse cruise speed. Now Denmark is flat, and on the few gradients I encounter, and with full load there is a tendency to shift down a bit earlier than before, but fully acceptable. Mind you I did tour Austria and Switzerland this summer, using this set-up, and it worked a treat.
TommoT

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Chazzyb
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G80 front sprocket

Post by Chazzyb »

quote:
Crawford initially said it was a 1959/61 G80S, as does his bio.


He may have done, but not in this thread. I regret I don't read all threads on the site, so didn't have any more information. I also don't make a habit of looking at the bios. If it's deemed necessary to read all threads and examine all bios before making a response here, there's something wrong. I would prefer, as I try to with any questions I post, for full 'qualification' information about the bike to be included. It will help avoid misunderstandings being made.

Charles
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Ludwig
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G80 front sprocket

Post by Ludwig »

quote:
Thanks ,both for your quick responses.On further detective work I find that there is a legitimate 23 tooth sprocket available for the alternator G80. Is this worth considering? Was it an AMC option? What would be the circumstances for its'fitting?Cheers,C.

Hi,
the 23 tooth sprocket was fitted for 18" - tyres (62 or so on), so the overall ratio ist nearly the same as 22 t. with 19" tyres.
Regards Ludwig
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crawsue
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G80 front sprocket

Post by crawsue »

Thanks all,that explains all the options.I'm relatively new to the marque and although I have "swatted up" on Roy Bacons excellent book I am still a bit behind the"8 ball".The change of wheel size had completely missed me!In the last 20 years or so all my tinkering has been with Jap or Hinkley stuff,where front sprocket wear meant final drive and was an easy fix(usually)and I assumed when I started this thread that I was going down that road.If I am reading TommoT 's contribution correctly, I can address the problem in either way.Comments on which way is simpler, and remembering Alan's comments about chain lengthening. I suppose that AMC never thought that 50 or so years later not giving their annual makeover a model "designation" would cause such identification aggro! In future I will make sure that I post with as much info as is available,having said that,my machine is alternator / magneto,which I don't think was ever a factory option??! Although I have been told by a few ,that it is the best option!
Hard work never killed anyone.....but why take the risk?
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