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 is believed to have originally been a Honda design. At some stage Honda used Kymco, a Taiwanese company, as a factory for Honda bikes. 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.

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,[1] 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.[1]

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.[1]

References
  1. "About GY6 Engines & Components". Archived from the original on 3 March 2016. Retrieved 17 February 2015.

Further reading
  • Chinese, Taiwanese & Korean Scooters 50cc Thru 200cc, '04-'09: 50, by Max Haynes and Phil Mather. Haynes Manuals. 2009.
  • Interfirm relations under late industrialization in China: the supplier system in the motorcycle industry; Volume 40 of I.D.E. occasional papers series. Moriki Ōhara. Institute of Developing Economies, Japan External Trade Organization. 2006. ISBN 9784258520404. p. 44, 53. Full text at HighBeam Research
  • The Little Book of Trikes By Adam Quellin. Veloce Publishing Ltd, 2011. ISBN 9781845842956. p. 64.
  • Scooters Service and Repair Manual. by Phil Mather and Alan Harold Ahlstrand. Haynes Manuals. 2006.
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