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Matchless G80 identification

Matchless G80 identification

Postby 3dcycle » Wed Jul 20, 2016 2:11 pm

Hi
I have a 1956 G80 Matchless that I just finished retiring as a dirt scrambler. I have assumed that it is a G80CS since the last part of the serial number is "C". It also has a competition magneto. Does anyone know how to correctly identify is it is a G80CS from the following serial numbers?
Engine 56/G80 2232C
Trans GB27M55
Frame 82853

3dcycle
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Re: Matchless G80 identification

Postby BillT » Thu Jul 21, 2016 7:05 pm

I have a 1961 G80CS. My serial is different from yours, but that is likely due to the different year.

As I understand it, 'CS' means competition sprung, which implies high-compression engine with competition magneto, and swing arm frame. I believe the G80CS did not exist as a customer model until 1955 or 1956, pretty much coinciding with the change to the Girling rear dampers and the 'AMC' gearbox.

If your bike has the swing arm rear suspension, high compression engine and competition (manual advance, red label) magneto, I should think it is a CS.

If your bike has a rigid frame (no swing arm), and a high compression engine, then it is a G80C. The 'C' variant was popular in the 50s, especially for scrambles and hillclimbs.

By the time my bike was produced, rigid frames were rapidly falling out of favor. The 'C' variant was not in the catalog in 1961.

I also think G80s ran sequential serial numbers throughout their production, and your 1956 is about 1900 before my '61.
'73 Norton 850 Commando - 3030xx
'69 Norton Ranger 750 - P11/1289xx
'67 Matchless G15CS - G15CS/1235xx
'61 Matchless G80CS - 61/G80CS/41xx
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BillT
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Location: Broward County, Florida

Re: Matchless G80 identification

Postby 3dcycle » Fri Jul 22, 2016 5:14 am

Thanks for your reply
My matchless has the competition magneto (NC1). When I had the top end rebuilt the gaskets were for an G80C. There wasn't much to this bike before I restored it into a vintage dirt tracker. Since the C is stamped as the last part of the engine serial stamp that it does designate it a a competition? I have photos of it on my blog site 3dcycle@blogsite.com. Thanks for your input

3dcycle
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Re: Matchless G80 identification

Postby BillT » Sat Jul 23, 2016 4:50 am

I believe the key differences between a G80 and G80C were competition magneto, aluminum cylinder barrel, bigger carb and higher compression.

AMC used a pretty comprehensive machine numbering system in those days, with model year of manufacture, model designation and sequential serial number stamped on the engine case. The variants of the G80 in the mid fifties were G80 (road bike, rigid frame), G80S (road bike, swing arm), G80C (competition, rigid frame) and G80CS (competition, swing arm).

Specs changed over the years, but the typical G80 had an iron barrel and around a 6:1 compression ratio. The G80C or G80CS had an alloy barrel and 7.5:1 or higher compression ratio (you could order your bike with different ratios, up to about 10.5:1, dependent on the year, and 19 or 21 inch front rim, whether you wanted to run scrambles or trials).
'73 Norton 850 Commando - 3030xx
'69 Norton Ranger 750 - P11/1289xx
'67 Matchless G15CS - G15CS/1235xx
'61 Matchless G80CS - 61/G80CS/41xx
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Location: Broward County, Florida

Re: Matchless G80 identification

Postby pierodn » Fri Nov 11, 2016 11:52 am

BillT wrote:I believe the key differences between a G80 and G80C were competition magneto, aluminum cylinder barrel, bigger carb and higher compression.

AMC used a pretty comprehensive machine numbering system in those days, with model year of manufacture, model designation and sequential serial number stamped on the engine case. The variants of the G80 in the mid fifties were G80 (road bike, rigid frame), G80S (road bike, swing arm), G80C (competition, rigid frame) and G80CS (competition, swing arm).

Specs changed over the years, but the typical G80 had an iron barrel and around a 6:1 compression ratio. The G80C or G80CS had an alloy barrel and 7.5:1 or higher compression ratio (you could order your bike with different ratios, up to about 10.5:1, dependent on the year, and 19 or 21 inch front rim, whether you wanted to run scrambles or trials).

Hi Bill,
I have a G80 C stamped on the frame with numbers 888.. and has the rear swinging arm and shock absorvers.
Pieo

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