monstergy6.com said:What is a GY6?
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), 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: Kymco, PGO (imported by Genuine Scooter Company in the USA), Ricardo Motors, Roketa, Strada, SUNL, Tank, Vento, Yamati, and many others.
I'd like to note that Honda had their parts made in china under their management and quality control and when they were done with with the GY6 and or the Honda mini bike design it was cheap and easy for for the Chinese manufacturers to buy the licenses and reproduce the parts and vehicles and to great success too.
monstergy6.com said:How do I know if I have a GY6?
If you look just under the left side engine cover, right above the kick stand, there will be a series of
engraved letters and numbers. If you see QMB139, then you have a 50cc GY6, if you see QMJ157, then you have a 150cc GY6 engine
scrappydogscooters.com said:Hey MO! How do I know what engine I have? I have heard all this talk about 1PE40QMB and 157QMJ blah blah. It seems so darn confusing to get parts for these Chinese bikes! What can you do to help? -Lost in Las Vegas.
Chinese bikes and ATV's can really be confusing, that is why scrappy dogs was started. There are two identifications to remember by using this site for help, not only to know what you have, but to get what you need. The first is the engine type. While this site uses a simplified directory at the left, you really need to know the engine number to get your parts right. This engine number is typically in two parts on the same stamp location. Most of the time the numbers are stamped on the left side of the engine, under the belt cover, near the front close to the engine mount to the frame. The bottom number is the reg. number, the top number is the one to pay attention to, this is the engine identification number. It tells you what you have. Below is a picture of a number plate for a 50cc 4stroke, also known as a 139QMB.
The engine number is very significant, and reveals alot. Take for example a popular engine, like the Honda Monkey (chinese copy) The number stamped on it is a 1P39FMB. The first number is the number of cylinders, the second, a P, is code for a horizontal engine. The next 2 numbers, 39, is the bore diameter in mm, 39mm bore. The next letter, F, indicates that it is natural (not forced) air-cooled style. The next letter designates that it is a motorcycle engine "M". The next letter reveals the full engine displacement. B is code for a 50. C for a 60, D for a 70, F for a 90, G for a 100, H for a 110, I for a 125, J for a 150, and so forth. Notice that the size graduation increase is indicated by an increment in the alphabetical letter? It's no coincidence. It's amazing to me the cooperation in standards of China. There is also prefix letters on many, designating the manufacturer, like Quinjiang (we have them all on file), which stamps there acronym, QJ, as the first two letters in there code. It's also very revealing, as the QJ139qmb is quite different then the other 139qmb's. It uses the 1E40qmb (2T) transmission components, and the engine case is a little different. There are also suffix numbers at the end, which designate iteration levels, like -3 in the photo below, which denotes that it is the third design, or improvment. Call or email us if you have any questions. We love to help. Here is the Chinese engine code chart with the example of the JOG 2stroke engine number 1PE40QMB-4
Some engines have the number plate on the upper rear side of the belt cover. GY6 engines are on the fron, bottom, left had side near the centerstand pivot. 2stroke JOG's are near the rear wheel like Honda Spree elite and DIO. They are often on a sticker on the belt case. Sometime the airbox needs to be removed and alot of grime washed off on the 2strokes. By federal law they are stamped on the engine case and are there, even if you don't see it at first inspection. Either way it will help you significantly to know this.
scrappydogscooters.com said:How do I know if my 150cc GY6 is a long or short case? I want to change my belt and it has no indication on it?
With a few exceptions, the 125/150 GY6 has two belt sizes: 743 for the short case, and 842 for the long. If you have a 10 inch rim on the rear with a tire that is 3.50 wide or less, it's a short case. The belt cover will also measure 16 inches from end to end. If you have a 10" rim with a 4.00 wide, or a 12 or 13" rim, you have a long case. The belt cover will measure 17 1/8" long. Another easy way to tell is simply to count the number of retaining bolts for the belt cover, the short case has 8, the long one has 10.
I did some measuring today and it seems this also applies to 50cc GY6 scooters as well.
scrappydogscooters.com said:QJ139QMB-3 and QJ1P39QMB-3 anomaly engine tech facts
Hey MO! I've got this QJ engine in my Baja Sun City SC50, it's also found in the Vento Triton, and MotoMojo Roadster 50. I'm just confused about what parts fit what?
Yes, that is a pretty unique engine. We call it the QJ anomaly. This engine is fundamentally the same, with these differences:
1) The aperture in the crankcase for the cylinder is slightly smaller, making big bore kits difficult without some modification
2) The belt size is unique, using the 836-17-30.
To confuse things a little, it seems the Vento and MotoMojo uses an 891-17-30 belt.
3) The QJ anomoly uses 21mm 2stroke JOG engine variators, rollers and rear clutch pulleys.
4) The belt cover is unique also
5) These are often fitted with disc brakes in the rear, making some of these components difficult to acquire.
6) The carburetors that are fitted on these use a different type than standard 139qmb. We would recommend changing the carb to the more common type.
Other than these differences, it is essentially a standard 139QMB engine.
scrappydogscooters.com said:MO, I've noticed that there are a few different heads types and other parts on GY6-125/150 engines. I thought they were all the same? All these engines had the 157QMJ in the engine code. What gives!
Yes, there are a few different types, but are easily distinguished, and thankfully most are interchangable. The standard GY6 engine parts your will find on our site fit and work perfectly. There are two variations that I will identify now.
GY6 Scooter Version B - This engine is found in alot of higher priced quality scooters like Zhen, Lance, Fly, etc. The engine number will be BN157QMJ, and will have a 16" rear wheel ( although some Lance Duke Tourings have the smaller wheel BN engines, which are standard parts, with some other exceptions). This engine is made by BenNeng of the Zhongneng Industry Group. This engine has alot of non-interchangable parts, like the variator, head, stator, etc. The head on these is taller than a standard GY6 head, and has longer valve stems. The stators are 12pole DC types. The belts are longer than standard, and are often 906. The cylinders however will fit from standard parts. Our big bore kits will fit -B models. The performance 4 valve head will fit these without use of the longer chain and retention studs, as this engine already has them.
GY6 ATV Version B - This engine is found almost exclusively in ATV, Buggy, and Go-Cart's. Externally they look identical to a standard GY6, with one prominent, yet subtle difference. They have two bolts holding the cam cover down, while the standard GY6 has 4. The other differences are internal, and on the top end only. The cylinder retaining studs are slightly wider spaced than a standard engine, not allowing the use of standard heads and cylinders. The apperature in the crankcase is larger than normal, which allows a larger big bore kit without machining of the case, but the kits that fit are nearly impossible to find. One last thing on Kazuma ATV engines, model KZM157QMJ. Nothing fits these except Kazuma specific parts. The QJ157QMJ and QJ156QMJ by Quinjiang is also a unique oddity.
monstergy6.com said:What is a CVT transmission?
Peer into a planetary automatic transmission, and you'll see a complex world of gears, brakes, clutches and governing devices. By comparison, a continuously variable transmission is a study in simplicity. Most CVTs only have three basic components:
* A high-power metal or rubber belt
* A variable-input "driving" pulley
* An output "driven" pulley
The variable-diameter pulleys are the heart of a CVT. Each pulley is made of two 20-degree cones facing each other. A belt rides in the groove between the two cones. V-belts are preferred if the belt is made of rubber. V-belts get their name from the fact that the belts bear a V-shaped cross section, which increases the frictional grip of the belt.
When the two cones of the pulley are far apart (when the diameter increases), the belt rides lower in the groove, and the radius of the belt loop going around the pulley gets smaller. When the cones are close together (when the diameter decreases), the belt rides higher in the groove, and the radius of the belt loop going around the pulley gets larger. CVTs may use hydraulic pressure, centrifugal force or spring tension to create the force necessary to adjust the pulley halves.
Variable-diameter pulleys must always come in pairs. One of the pulleys, known as the drive pulley (variator), is connected to the crankshaft of the engine. The driving pulley is also called the input pulley because it's where the energy from the engine enters the transmission. The second pulley is called the driven pulley because the first pulley is turning it. As an output pulley, the driven pulley transfers energy to the drive shaft.
When one pulley increases its radius, the other decreases its radius to keep the belt tight. As the two pulleys change their radii relative to one another, they create an infinite number of gear ratios -- from low to high and everything in between. For example, when the pitch radius is small on the driving pulley and large on the driven pulley, then the rotational speed of the driven pulley decreases, resulting in a lower “gear.” When the pitch radius is large on the driving pulley and small on the driven pulley, then the rotational speed of the driven pulley increases, resulting in a higher “gear.” Thus, in theory, a CVT has an infinite number of "gears" that it can run through at any time, at any engine or vehicle speed.
monstergy6.com said:What is an AC or DC CDI?
CDI modules can be generally divided into two:-
* AC-CDI - The AC-CDI module obtains its electricity source solely from the alternating current produced by the alternator. The AC-CDI system is the most basic CDI system which is widely used in small engines.
* DC-CDI - The DC-CDI module is powered by the battery, and therefore an additional DC/DC inverter circuit is included in the CDI module to raise the 12 V DC to 400 V DC, making the CDI module slightly larger. However, the vehicle that uses DC-CDI system has more precise ignition timing and the engine can be started easier when cold.
scrappydogscooters.com said:AC/DC CDI Comparison