| MODEL | AJS MODEL 18 500 (S, CS, STATESMAN) 1945 - 1966 |
| Year | 1945 - 1966 |
| Engine Type | Single cylinder, 2 valves per cylinder, pushrod OHV |
| Displacement / Capacity | 498 cc / 30.4 cu in |
| Bore X Stroke | 82.5 x 93 mm |
| Compression Ratio | 6.9:1 (with compression plate); 7.24:1 (without) |
| Cooling System | Air cooled |
| Max Power | 20.9 kW / 28 hp @ 5600 rpm |
| Max Torque | — |
| Ignition | Lucas magneto |
| Induction | Carburettor, type 89B/IAK |
| Start System | Kick |
| TRANSMISSION SPECS | |
| Lubrication | Dry sump |
| Gear Box | 4-speed, Burman gearbox |
| Clutch | — |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | — |
| Front Suspension | Hydraulic telescopic fork |
| Rear Suspension | Swingarm, twin shock |
| Front Brakes | Drum |
| Rear Brakes | Drum |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | 760 mm / 30 in |
| Wheelbase | 1400 mm / 55 in |
| Ground Clearance | — |
| Dry Weight | — |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | 3.25-19 |
| Rear Tyre | — |
| FUEL SYSTEM | |
| Fuel Capacity | — |
| Fuel Consumption | — |
| Top Speed | — |
Photo: AlfvanBeem, CC0, via Wikimedia Commons
Photo: AlfvanBeem, CC0, via Wikimedia Commons
A 1930s-derived 500 single that stayed in production for roughly thirty years. The rigid frame gave way to a sprung rear end on the 1949 18S, shocks evolved from the early candlestick type to Jampot and then Girling units, and alloy heads and higher compression followed in the 1950s. The CS was the competition version, and the last short-stroke Model 18s marked the end of AJS singles when AMC merged with Norton and turned to twins.
