AJS Model 18500 (S, CS, Statesman)

AJS Model 18500 (S, CS, Statesman)
Manufacturer	AJS
Production	1945 - 66
Engine	Single cylinder, 2 valve per cylinder, pushrod OHV
Compression ratio	6.90:1 (with compression plate) 7.24:1 (with no compression plate)
Ignition	Lucas magneto
Transmission	4 Speed, Burman gearbox
Suspension	Front: Hydraulic telescopic fork Rear: Swinging arm, dual shocks
Brakes	Front: Drum Rear: Drum
Front Tire	3.25 -19
Rear Tire	34.25 -19
Wheelbase	1400 mm / 55 in
Seat Height	760 mm / 30 in
Weight
Oil Capacity	2.3 L / 4.8 US pt
Fuel Capacity	Rigid, Spring frame: 13 L / 4.23.4 US gal Competition: 10.2 L / 2.7 US gal
Manuals	Service Manual

Engine

The engine was a Air cooled cooled Single cylinder, 2 valve per cylinder, pushrod OHV. The engine featured a 6.90:1 (with compression plate) 7.24:1 (with no compression plate) compression ratio.

Chassis

It came with a 3.25 -19 front tire and a 34.25 -19 rear tire. Stopping was achieved via Drum in the front and a Drum in the rear. The front suspension was a Hydraulic telescopic fork while the rear was equipped with a Swinging arm, dual shocks. The Model 18500 (S, CS, Statesman) was fitted with a Rigid, Spring frame: 13 L / 4.23.4 US gal Competition: 10.2 L / 2.7 US gal fuel tank. The wheelbase was 1400 mm / 55 in long.

Photos

AJS Model 18500 (S, CS, Statesman)

Overview

The AJS Model 18 was developed from a design from the 1930s, despite which it was still being manufactured 30 years later. The AJS was updated when a springer frame rear suspension was made available for 1949, to become the Model 18S. The suspension was a vast improvement on the rigid rear end - which had given a bouncy ride. Each of the two 'Candlestick' shocks held only 50 cc of SAE 20 weight oil. They were prone to leaks and were replaced by the larger diameter 'Jampot' shocks on the 1951 version. The engine was released just postwar with a compression ratio of 5.9:1, necessary because of the low quality fuel available in Britain immediately after the War. British singles were designed to make the best of the fuel available. Post war petrol rationing continued until 1950 and it was several years before performance fuels were generally available in the UK. The Model 18’s low compression did mean it was easy to start[1] and The model 18:s had better performance and fuel economy than the fast cars of the time.

By 1951 the model 18 had an alloy cylinder head and the competition models had also an alloy cylinder (with steel liner in it), where the barrel fins went all the way to the base. The magneto was moved in front of the cylinder on the Matchless G80 for 1952. The earlier model did not have a magdyno - the separate magneto was directly above the dynamo behind the cylinder. The leaky pressed-steel primary chain-case that first appeared in early times had a small clutch inspection/adjustment plate added in 1952 and in 1954 the whole clutch dome was replaceable in it. The compression ratio was increased to 8.7:1 in 1956 and in 1958 an alloy cover primary chain-case became available. The unreliable 'jampot' shock absorbers were replaced with Girling shocks in 1956 and in 1957 AMC switched from Burman gearboxes to their own make. In 1960 the model 18 gained a duplex frame. The 500 cc "long stroke" AJS 18CS was produced from 1951 through 1955. In 1956 it was replaced by the shorter stroke, larger bore models that used the same numeric codes. The bore of these early models was 82.5 mm (3.25 in), while the 1956 through 1966 "short stroke" (final version) models had a bore of 86 mm (3.39 in). The C was 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 The AJS and Matchless singles were doomed when AMC merged with Norton as all production was transferred to twins cylinder bikes - so the short-stroke Model 18 is the end of an era. Source

Make Model.	AJS Model 18 500 (S, CS, Statesman)
Year	1945 - 66
Engine Type	Single cylinder, 2 valve per cylinder, pushrod OHV
Displacement	498 c / 30.4 cu in
Bore X Stroke	82.5 x 93 mm
Compression	6.90:1 (with compression plate) 7.24:1 (with no compression plate)
Cooling System	Air cooled
Lubrication	Dry sump
Oil Capacity	2.3 L / 4.8 US pt
Induction	Carburetor, type 89B/IAK
Ignition	Lucas magneto
Starting	Kick
Max Power	20.9 kW / 28 hp @ 5600 rpm
Transmission	4 Speed, Burman gearbox
Drive	Chain
Front Suspension	Hydraulic telescopic fork
Rear Suspension	Swinging arm, dual shocks
Front Brakes	Drum
Rear Brakes	Drum
Wheels	Steel, wire spokes
Front Tire	3.25 -19
Rear Tire	34.25 -19
Wheelbase	1400 mm / 55 in
Seat Height	760 mm / 30 in
Dry-weight	Standard rigid frame: 15660 kg / 353 lbs Spring frame: 175 kg / 386 lbs Competition rigid frame: 137 kg / 303 lbs
Fuel Capacity	Rigid, Spring frame: 13 L / 4.23.4 US gal Competition: 10.2 L / 2.7 US gal

External Links

• http://en.wikipedia.org/wiki/AJS_18