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GY6 is a designation given to an engine design commonly used in scooters and ATVs of Asian design.
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[edit] Configuration
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 stroke. 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 VDP-type continuously variable transmission using a rubber belt. 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.
[edit] Variants
GY6 engines are generally found in displacements slightly less than 150 cc, 125 cc, or 50 cc.
GY6 engines are manufactured with a variety of different swingarm lengths and styles. Most common are the "short case" and "long case" style. The short case GY6 offers just enough clearance to mount a standard 10-inch tire and rim, while the long case version typically will provide enough clearance for a 12-inch tire and rim, or 13-inch rim with low-profile tires. Recently, extra long GY6 variants have appeared, allowing a 16-inch wheel and tire to mount up. A drum brake is typically integrated into the swingarm, as many scooter wheels have an integral drum. Some variants, however, provide a mounting point for a disc brake caliper instead of the drum brake hardware. ATV applications generally mount the swingarm fast to the frame, with a sprocket for chain drive in place of the rear wheel, and exclude the brake provisions entirely.
Specifications of GY6 variants (Lifan manufactured)[1]
| Engine | Displacement | Power | Bore x Stroke | Compression Ratio |
|---|---|---|---|---|
| 139QMB | 49.5 cc | 2.95 hp (2.20 kW) at 7,500 rpm | 39 × 41.4 mm (1.54 × 1.63 in) | 10.5:1 |
| 152QMI | 124.65 cc | 6.8 hp (5.1 kW) at 7,000 rpm | 52.4 × 57.8 mm (2.06 × 2.28 in) | 9.2:1 |
| 157QMJ | 149.6 cc | 8.6 hp (6.4 kW) at 7,000 rpm | 57.4 × 57.8 mm (2.26 × 2.28 in) | 8.8:1 |
The GY6 engine family is produced by a wide range of manufacturers throughout Asia, and as such there may be many small differences between engines from different firms.
[edit] Use
Engines with the GY6 design, as of October 2010[update], are being produced and used today by many manufacturers in a variety of scooters and ATVs.[citation needed] These include Taiwanese brands such as Kymco, SYM, PGO (imported by Genuine Scooter Company in the USA), and Adly. Many Chinese manufacturers also use engines with the GY6 design, such as Neco, Qianjiang, Zongshen, and Xingyue. These manufacturers are sold in the USA under many different brands, such as Roketa, Strada, Tank, SUNL, Vento, and Yamati.
