The GY6 engine is a 4 stroke engine with a simple design and is a HONDA COPY (see below for more Honda info). What makes this engine so widely used in so many applications is due to the CVT or CONSTANT VELOCITY TRANSMISSION. This CVT is a belt driven style engine and is easily identified by the large belt cover located on left side of engine. VERY POPULAR ENGINE used in Scooters, Mopeds, ATVs and the most popular engine for use in GO KARTS. The GY6 engine delivers good low end torque and wide powerband and that is another reason the engine is so widely used in many, many powersports applications.
Bore size is always 57mm, however there is a couple of variations in cylinder jugs, cylinder heads and gaskets used. We can help identify which version you have rather easily. Another version is used by KAZUMA. If you have an engine stamped KAZUMA on the side---some parts are exclusive for that engine.
The best service manual we have found is the Yerf Dog Go Kart Manual. Best of all its FREE DOWNLOAD. There is also a great GY6 150 Engine Top End Rebuild-Overhaul Manual and is also FREE DOWNLOAD.
In simple terms---we stock 3 different head gaskets for the GY6 150cc engine. Do not be fooled by others that state all are the same.
The following is from WIKIPEDIA.com:
The Honda GY6 Engine is a small four-stroke internal combustion engine developed by the Honda Motor Company. The GY6 is commonly used to power various kinds of small vehicles, including ATVs and scooters. The Honda Motor company has been said to have perfected the scooter engine design in the 1960s. Building upon that technology a newer motor, the Honda gy6 engine, was produced in the 1980s. This is a 4 stroke single cylinder, air or oil cooled design that comes standard with two overhead valves. Stock horsepower ratings can be found quoted in the range of 7.8 hp (5.8 kW) to 12.4 hp (9.2 kW). The engine is capable of producing 12,000 rpm and power upwards of 14 horsepower (10 kW) with modifications according to end users. The GY6 engine has a built in swing arm with automatic CVT transmission that is belt driven. This engine was originally manufactured in 50 cc (3.1 cu in), 125 cc (7.6 cu in), and 150 cc (9.2 cu in) engine sizes and was found in the Honda Elite and Spacey line of motor scooters. Honda no longer uses this design on their scooters, but Chinese, Korean, and Taiwanese copies of this engine are readily available. Current brands of import scooter lines that use the Honda GY6 cloned engine technology include: e-GO Motors - TriPOD (tilting three wheeler), Xingyue, Flyscooters, Kymco, PGO (imported by Genuine Scooter Company in the USA), Ricardo Motors, Roketa, Strada, SUNL, Tank, Vento, Yamati, among others. With the wide availability and cheap cost of this engine, Asian ATV manufacturers have started to use this powerplant in their youth line of ATVs (quads) and buggies (off road go karts and trail buggies) 150 cc youth quads that contain the GY6 powerplant are found being imported under many brands including Ricardo Motors, Yamoto, Kazuma, and Redcat. Off road buggies and full suspension go karts that include this style of engine include Carter Brothers Talon Line, Carter Brothers XTV, TJ Powersports Twister Hammerhead, Dazon Raider, Kasea Adventure Buggy, Blade Powersports 150 cc, Tomberlin Punisher & Crossfire, Baja Motorsports Dune 150. With the wide availability of this engine in both older Honda products and newer Asian imports there is a vast amount of information, modifications, and performance parts available to the end user.