Engineered by AJS for the sport motorcycle segment, the 2011 AJS NAC12 125 relies on a 124 cc (7.6 cu in) liquid-cooled twin, four-stroke powerplant. In factory specification, peak output is rated at 11.4 HP (8.3 kW) at 10,500 rpm, transferring power to the rear wheel through a 5-speed gearbox and chain final drive. With a specific output of 91.9 HP per liter, the engine character is indicating a tractable, stress-free state of tune focused on everyday usability and broad torque delivery.
On the scales, the NAC12 125 measures 168 kg (370 lbs) wet (curb), translating to a power-to-weight ratio of 0.07 HP/kg (14.74 kg per horsepower). Rider ergonomics and chassis geometry center around a 770 mm (30.3 in) seat height — offering a neutral standover height that accommodates most average-inseam riders without sacrificing cornering clearance, combined with a 1,510 mm (59.4 in) wheelbase engineered for balanced agility and highway composure. The 18-liter (4.8 US gal) fuel tank supports practical everyday commuting and weekend road stints.
Within MotoLibrary's AJS archive, this model family spans 2 indexed model years from 2010 to 2011, allowing buyers to track year-over-year changes in emissions tuning, weight and equipment.
Specific Output
91.9 HP/L
Power-to-Weight
0.07 HP/kg (14.74 kg/HP)
Standover Height
770 mm (30.3 in)
Engine
Displacement124.0 ccm (7.57 cubic inches)
Engine TypeTwin, four-stroke
Engine DetailsTwin, four-stroke
Power11.4 HP (8.3 kW)) @ 10500 RPM
Bore x Stroke44.0 x 40.0 mm (1.7 x 1.6 inches)
Fuel SystemCarburettor
IgnitionCoil CDI
CoolingLiquid
Transmission
Gearbox5-speed
Final DriveChain (final drive)
ClutchWet, multiplate
Performance
Emission DetailsEuro 3
Chassis
Front SuspensionTelescopic fork
Rear SuspensionTwin reservoir shocks
Wheelbase1510 mm (59.4 inches)
Wheels & Brakes
Front Tyre90/90-18
Rear Tyre130/90-15
Front BrakesDouble disc
Rear BrakesSingle disc
Dimensions & Weight
Dry Weight153.0 kg (337.3 pounds)
Weight incl.168.0 kg (370.4 pounds)
Power/Weight0.0744 HP/kg
Seat Height770 mm (30.3 inches) If adjustable, lowest setting.
Use this page to compare this motorcycle by its real specifications, not only by model name. Focus on the details that affect fit, comfort, handling, range and ownership.
Power
Compare engine output with similar motorcycles if acceleration, highway use or two-up riding matters.
Seat Height
Check the seat height against your inseam and riding posture before choosing a motorcycle.
Weight
Compare weight carefully because it affects low-speed handling, parking and confidence.
Fuel Capacity
Fuel capacity helps estimate touring range and how often you may need to stop.
Brakes
Brake setup is worth comparing if you ride in traffic, mountains or with a passenger.
Suspension
Suspension details can matter for comfort, road feel and long-distance riding.
Transmission
Transmission and final drive affect maintenance, smoothness and everyday usability.
