C90 K3

1978 Honda C90 K3 Technical Analysis & Specification Breakdown

Engineered by Honda for the scooter motorcycle segment, the 1978 Honda C90 K3 features a 89 cc (5.4 cu in) air-cooled single cylinder, four-stroke configuration. In factory specification, peak output is rated at 7.5 HP (5.5 kW) at 9,500 rpm while maximum torque reaches 6 Nm (4.4 lb-ft) at 6,000 rpm, transferring power to the rear wheel through a 3-speed gearbox and chain final drive. With a specific output of 84.3 HP per liter and a 3,500 rpm working window between peak torque (6,000 rpm) and peak power (9,500 rpm), the engine character is indicating a tractable, stress-free state of tune focused on everyday usability and broad torque delivery.

On the scales, the C90 K3 measures 91.6 kg (202 lbs) wet (curb), translating to a power-to-weight ratio of 0.08 HP/kg (12.21 kg per horsepower). Rider ergonomics and chassis geometry center around a 790 mm (31.1 in) seat height — offering a neutral standover height that accommodates most average-inseam riders without sacrificing cornering clearance, combined with a 1,190 mm (46.9 in) wheelbase engineered for quick, flickable steering geometry. The 5.5-liter (1.5 US gal) fuel tank paired with a rated consumption of 2.5 L/100 km provides an estimated theoretical range of roughly 220 km (137 miles) between fill-ups, while factory top speed is listed at 80 km/h (50 mph).