Clutch and Throttle - The clutch and throttle, which controls engine speed, are operated by twist-type controls on the handgrips. A lever near the handgrip controls the front-wheel brake; a foot pedal engages the rear-wheel brake. Except on very small machines, the front brake is usually of the hydraulic disc type. The rear brake may be disc or drum. An electric push-button starter has mostly replaced the kick-starter.

Springs - These absorb the jolts caused by the irregularities of the road surface or other obstacles that are encountered while on the roads.

›› Kinds of springs

(1) parallelogram suspension, which is a somewhat clumsy system because the whole mass of the front wheel and fork participates in the oscillation

(2) telescopic front forks in combination with short swinging arm, in which arrangement the oscillating mass is reduced

(3) telescopic front forks in combination with long swinging arm : more resilient than the foregoing, but involving great oscillating mass (the same principle is applied to the rear wheel suspension). The telescopic suspension system used in types (2) and (3) has the advantage that it can undergo considerable compression in conguide with only small oscillating masses. By these or similar means it is possible to achieve very efficient suspension conditions, so that the saddle springing can be dispensed with on modern motor cycles.

(4) A foam-rubber seating cushion is usually sufficient, especially on racing machines. Spring elements in combination with oil- filled cylinders provide the necessary shock-absorbing function.

Engines - Two-stroke and four-stroke engines are used as power units for two-wheelers. The power is transmitted to the rear wheel through the gearbox and thence through sprockets and chains or through a drive shaft. Transmission is through a shaft , the shaft being neatly accommodated in the swinging arm of the rear suspension. Motor cycles and mopeds have wire-spoke wheels, whereas scooters generally have solid wheels like those of a car.