Matchless G80

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The Matchless G80 / AJS Model 18 was a single cylinder 500 cc motorcycle built by Associated Motorcycles (AMC) from 1949 to 1966. During the 1950s and 60s the main export product for AMC was the AJS/Matchless range - the road bikes were very similar, often with only the badges distinguishing one marque from the other.

1 Matchless G80 / AJS Model 18 (1949 - 1966)
2 Sources

[edit] Matchless G80 / AJS Model 18 (1949 - 1966)

1949 Matchless G80S at auction in Las Vegas in 2007

In the early fifties the most popular British four-strokes were still pushrod singles. 500 cc machines typical of this era were the Matchless G80 and the AJS Model 18, both manufactured by Associated Motor Cycles (AMC). Both were made in the same factory, differing only in badging, and the position of their chain-driven magnetos.^[1] The earliest G80 is sometimes referred to as a G80L, the L signifying "Teledraulic" forks, rather than girder forks.^[2]

The magneto on an AJS was in front of the cylinder, and the Matchless magneto was behind. A design originating in the 1930s, the Matchless was updated with a spring frame (sprung-heel) rear suspension, becoming the G80S. The suspension was a vast improvement on the bouncy rigid rear end but wheel travel was limited.^[1]

AMC then adopted Velocette's twin-shock swingarm rear suspension design for its top models. Shorter vertical shock absorber units were introduced in 1949. The initial 'Candlestick' shocks held only 50 cc of SAE 20 weight oil. Leak prone, they were replaced by the 'Jampot' shocks in 1951.^[1]

The leaky pressed-steel primary chain-case first appeared on the 1953 G80S. In 1958 an alloy cover primary chain-case became available.

[edit] The G80/Model 18 Engine.

The motor was released with a compression ratio of 5.9:1, because of the poor quality fuel available in Britain immediately after the War.^[1] In 1949 the hairpin valve springs were back, after the use of conventional coil valve springs in wartime models. By 1951 the G80 had an alloy cylinder head, and the barrel fins now went all the way to the base. The compression ratio was increased to 7.3:1 in 1956.

Low compression meant that it was easy to kick-start and was more flexible at low revs. The earlier long stroke version might not quite reach 80 mph but it could trundle along at less than 20 mph in top gear. It also gave good fuel economy.^[1]

[edit] Technical Data

Production : 1949-1966
Engine type : Single cylinder, pushrod 2 valve, 4 stroke
Capacity : 498 cc
Bore and Stroke : “Long Stroke” 82.5 mm x 93 mm (1949-1955), “Short Stroke” 86 mm x 86 mm (1956-1966).
Compression Ratio : (1949 - 1955) 5.9:1, (1956 on) 7.3:1
Fuel System : 27 mm Amal Carburettor
Power : (1949 - 1955) 23PS @ 5,400 rpm
Dry weight : (1949 - 1955) 177 kg
Top Speed : (1949 - 1955) 78 mph^[1]

[edit] Model variations

The 500 cc "long stroke" G80CS and its AJS version, the 18CS were produced from 1951 through 1955. In 1956 they were replaced by the shorter stroke, larger bore models that used the same numeric codes. The bore of these early G80CS's was 82.5 mm (3.25"), while the 1956 through 1966 “short stroke” (final version) models had a bore of 86 mm. The C is for Competition (Scrambles) and the S for Suspension (not a rigid rear frame).

Engine numbers usually start with the year of production, followed by model designation, and completed with the production number of the motorcycle.