GY6 engine

The GY6 engine design is a four-stroke single-cylinder in a near-horizontal orientation that is used on a number of small motorcycles or scooters made in Taiwan, China, and other southeast Asian countries. It has since become a generic technology. Kymco went on to produce Honda clones such as the Pulsar (CB125), made to Honda standards, as part of their range.

Honda's KCW125 (the commercial name in Japan is "Spacy") was modified by Taiwan's Kwang Yang Motor Co., Ltd. (KYMCO), under Honda's consultancy, and became a standard model called the GY6, which various Taiwan makers imitated and minor-changed. Apparently, vehicles of this model were imported from Taiwan by various manufacturers and traders, and spread mainly in the southern coastal regions of China.

Configuration
The GY6 single is forced-air-cooled, with a chain-driven overhead camshaft and a crossflow hemi cylinder head. Fuel metering is by a single constant-velocity style sidedraft carburetor, typically a Keihin CVK clone or similar. Ignition is by capacitor discharge ignition (CDI), with a magnetic trigger on the flywheel. Because the trigger is on the flywheel instead of the camshaft, the ignition will fire on both the compression and exhaust strokes, making it a wasted spark ignition. An integrated magneto provides 50 V AC power for the CDI system and 20-30 V AC rectified and regulated to 12 V DC for chassis accessories such as lighting and to charge a battery.

It includes an integrated swingarm, which houses a centrifugally-controlled continuously variable transmission (CVT) using a rubber belt sometimes called a VDP. At the rear of the swingarm, a centrifugal clutch connects the transmission to a simple integral gear-reduction unit. There is no clutch of any kind between the CVT and the crankshaft; it is engaged via a centrifugal clutch at the rear pulley in the same fashion as Vespa Grande, Bravo, and variated Ciao model, as well as Honda Camino/Hobbit scooters/mopeds. An electric starter, backup kick-starter, and rear brake hardware is also housed in the swingarm.