GY6 engine

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The GY6 engine was originally developed by Honda for use in its motor scooters.[1] It was later adopted by many light vehicle manufacturers across China and South East Asia.


The GY6 design is a single-cylinder, four-stroke engine, in a near horizontal orientation. It is forced-air cooled, with a chain-driven overhead camshaft and a crossflow hemi head. Fuel metering is by a single constant-velocity style sidedraft carburetor,[2] typically a Keihin CVK clone or similar.

Ignition is by CDI, with a magnetic trigger on the flywheel. Because the trigger is on the flywheel instead of the cam, the ignition will fire on both the compression and exhaust strokes. An integrated magneto provides 12 v power for the CDI system, chassis accessories (such as lighting), and to charge a battery.[2]

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 permanently engaged. An electric starter, backup kick-starter, and rear brake hardware is also housed in the swingarm.[2]


Specifications of GY6 variants[3][4]

Engine Displacement Power Bore × stroke Compression ratio
139QMB 49.5 cc (3.02 cu in) 2.95 hp (2.20 kW) at 7,500 rpm 39 mm × 41.4 mm (1.54 in × 1.63 in) 10.5:1
152QMI 124.65 cc (7.607 cu in) 6.8 hp (5.1 kW) at 7,000 rpm 52.4 mm × 57.8 mm (2.06 in × 2.28 in) 9.2:1
157QMJ 149.6 cc (9.13 cu in) 8.6 hp (6.4 kW) at 7,000 rpm 57.4 mm × 57.8 mm (2.26 in × 2.28 in) 8.8:1

The GY6 engine is made by many different manufacturers in Asia, so there are many small differences between the engines.


  1. ^ "HONDA GY6 ENGINE 50cc to 150cc". GOKARTS USA. Retrieved 16 February 2015. 
  2. ^ a b c "About GY6 Engines & Components". Retrieved 17 February 2015. 
  3. ^ "La verdadera historia del Motor GY6". 27 October 2011. Retrieved 17 February 2015. 
  4. ^ "MOTORCYCLE ENGINE-Products World— 1P39QMB 1P39QMB". Retrieved 11 September 2015. 

Further reading[edit]

  • 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.