Motor Trike

Overview

A motor trike is a three-wheeled powered vehicle that keeps the front-end controls, riding posture, and powertrain of a heavyweight touring motorcycle while replacing the single rear wheel with a two-wheel driven axle. The result rides like a motorcycle from the saddle but stands upright at rest, so the rider never balances the machine at a stop. Most trikes are built either as factory models or as conversions, where a fabricator removes the swingarm and rear wheel of a donor cruiser and bolts in a live rear axle with a differential.

The machine centers on a V-twin engine driving through a multispeed driveline to the rear wheels. A telescopic front fork carries the single steered wheel, and a tubular frame ties the front motorcycle section to the fabricated rear trike body. Riders choose trikes for stability, for the ability to carry a passenger and luggage without low-speed balancing effort, and for accessibility when a two-wheeler is no longer practical.

Engine and combustion

The V-twin engine is typically an air-cooled 45-degree twin of 1700 to 1900 cc. Two cylinder barrels are bolted to a shared aluminum crankcase, and each carries a forged piston connected to a single-pin forged crankshaft. Overhead valves in each cylinder head are opened by pushrods riding a central camshaft, with rocker arms transferring motion to the poppet valves. A spark plug in each head ignites the charge.

The long-stroke twin produces high torque at low engine speed, which suits the heavier rolling mass of a three-wheeler. Combustion heat is rejected through deep cooling fins cast into the barrels and heads, with engine oil acting as a secondary coolant routed through an external cooler on many models.

Driveline and rear axle

Power leaves the crankshaft through a wet multiplate clutch into a constant-mesh gearbox of five or six speeds. The shift drum and forks select gear pairs in sequence as the rider works the foot lever. From the gearbox, a drive shaft carries torque rearward to the rear differential, which uses a ring-and-pinion gear set and spider gears to split torque between the two rear wheels. The differential is what lets the outer wheel turn faster than the inner wheel during a turn, preventing the tire scrubbing and steering resistance that a locked axle would cause.

The rear axle assembly is a beam housing carrying two half-shafts, each driving a rear wheel on a pair of ball bearings. The axle is sprung on leaf springs or coil units to absorb road shock and keep both rear tires loaded.

Front end, steering, and frame

The front steering assembly retains the motorcycle layout: two fork tubes clamped by a triple clamp that pivots in the steering head on tapered bearings. The single front wheel steers the vehicle, and the handlebar cluster houses the throttle, switch pods, and brake master cylinders.

The frame joins the original main frame tube to a fabricated rear subframe that supports the axle and bodywork. Conversion builders weld a conversion swingarm or fixed mount to locate the axle precisely, since trike handling depends on the rear wheels staying square to the frame.

Brakes and electrical

The brake system uses a hydraulic disc and caliper at all three wheels. Two master cylinders, one at the lever and one at the foot pedal, pressurize the circuits. An optional ABS modulator reads wheel speed and pulses the calipers to prevent lockup, which matters on a vehicle where a locked rear can upset the wide track.

The electrical system carries a 12-volt battery charged by the engine stator. The engine control unit meters fuel through the injectors and times the ignition coils. A wiring harness feeds the lighting set of headlamp, tail lamps, and indicators.

Bodywork and variants

The bodywork adds fenders over each wheel, a two-up seat with backrest, and a lockable rear trunk for touring luggage. Touring trikes lean toward large fairings and audio, while bobber and chopper conversions strip the bodywork down. Independent rear suspension variants replace the solid beam axle with two separately sprung half-axles for a smoother ride, at higher cost and complexity. Electric and reverse-gear options are common on touring models, since the heavy machine is hard to push backward by hand. Trike kits sold for self-installation include the axle, subframe, and bodywork matched to a specific donor model, while factory trikes integrate the rear section into the design from the start for cleaner styling and better weight distribution. Whichever route the build takes, the engineering priorities stay the same: keep the two rear wheels square to the frame, share braking across all three wheels, and keep the heavy axle assembly sprung so the ride stays controlled when loaded with a passenger and luggage.