The GY6 engine was originally developed by Honda for use in its motor scooters. 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, 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.
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.
EngineDisplacementPowerBore × strokeCompression ratio 139QMB49.5 cc (3.02 cu in)2.95 hp (2.20 kW) at 7,500 rpm39 mm × 41.4 mm (1.54 in × 1.63 in)10.5:140QMB E40QMB 1E40QMB 1PE40QMB BW1P50QMG97cc4.3 at 7000 rpm kw/rpm50mm x 49.5 mm (1.96 in x 2.04 in)9.5:11P50QMG97 cc4.3 at 7000 rpm kw/rpm50mm x 49.5 mm (1.96 in x 2.04 in)9.5:11P52QMI124.65cc (7.607 cu in)6.9 hp (5.2kw) at 7000 rpm52.4 mm × 57.8 mm (2.06 in × 2.28 in)9.2:1BW1P52QMI124.65 cc (7.607 cu in)5.8 hp at 7000 rpm52.4 mm × 57.8 mm (2.06 in × 2.28 in)9.5:1152QMI124.65 cc (7.607 cu in)6.8 hp (5.1 kW) at 7,000 rpm52.4 mm × 57.8 mm (2.06 in × 2.28 in)9.2:1BW1P57QMJ149.6 cc6.6 hp at 7500 rpm57.4 mm × 57.8 mm (2.26 in × 2.28 in)9.5:11P57QMJ149.6 cc (9.13 cu in)8.6 hp (6.4 kW) at 7,000 rpm57.4 mm × 57.8 mm (2.26 in × 2.28 in)8.8:1157QMJ149.6 cc (9.13 cu in)8.6 hp (6.4 kW) at 7,000 rpm57.4 mm × 57.8 mm (2.26 in × 2.28 in)8.8:1LB1P57QMJ149.6 cc (9.13 cu in)8.9 hp (6.8 kW) at 7,000 rpm57.4 mm × 57.8 mm (2.26 in × 2.28 in)8.8:1161QMK168.8 cc9.8 hp at 7000 rpm61 mm x 57.8 mm (2.40 in x 2.28 in)9.2:11P63QML180cc6.5 kw/7000RMP If you have any of the missing info in the chart or a correction, please share.