The GY6 is a one-cylinder, four-stroke scooter and all-terrain vehicle engine whose origin remains a subject of debate. Many believe the GY6 is of Honda origin, first developed in the 1960s, but the true originator of the GY6 engine is not agreed upon. Currently, Honda no longer uses the GY6 engine on its products, but it is found on a multitude of Asian-manufactured scooters from many different companies. Identification of the GY6 scooter engine relies on finding and translating the engine code, which provides particular engine specifications.
Locate the GY6 engine code. The engine code is normally found on the side of the engine, below the oil drain plug. It is below the converter, or CVT, belt cover. The six-position engine code, "157QMJ," for example, describes the engine particulars and has no GY6 or manufacturer designation.
Decipher the first three positions of the GY6 engine code. According to the Buggy Depot website, the first position of the code "157QMJ" is the cylinder count. All GY6 engines have one cylinder. The second and third positions are the cylinder bore measurement. The code "57" is a 57-mm cylinder bore.
Decode the three remaining positions of the GY6 engine code. Position "Q" is the engine style -- all GY6 engines have the "Q" designation in the fourth position. Positions five and six refer to the engine displacement. The second letter of this section ascends alphabetically for each 10 cubic centimetres of displacement -- "MB" is a 50 cubic-centimetre engine, while "MC" is a 60 cubic centimetre and "MD" is a 70 cubic-centimetre engine.
It is common to find a series of numbers below the engine code. These numbers are likely sequential production numbers, and there is no way of decoding them.