The Chinese scooters using the Honda Clone GY6 engines lend themselves to a complete line of upgrades that will get the kind of performance you can use to commute in traffic and safely get around for very affordable scooter. Here are some ways to get this done. These engines are also used in Kymco, SYM, PGO, TNG, QLink, Peirspeed, Schwinn along with Linhai, Roketa, Tank, Keeway, JMSTar, Jonway, Wangye, Motofino, to list them all would take for ever. Scootertronics opened shop in 2003.
This info covers both GY6 Engines for 50 (49cc) and 150 (147cc)
This page continues to be upgraded.
We will cover all the different areas from more speed and power to shocks and windshields. The list will grow as we go along, please feel free to call us if there is something we are covering you need more info on or you have questions about upgrades.
Use this list so you have somewhere to start, upgrades can be done to the following
Fuel and Air
Electrical
Engine
Exhaust
Transmission
Shocks
Windshields
Trunks Top Cases Rear Carrier
Brakes, Calipers, Disc
Tires
Fuel and Air
Get the materials to your engine to produce fire to move piston that moves the crank shaft which gets power to trans and wheels.
From the start good quality fuel and air lines along with fuel valve and gas and air filter do the delivery to the carb with a larger main jet and free flow air filter plus carbs and intakes get whats needed in the right amount through the carb. You can replace the following to achieve this upgrade and bear in mind these just might fix a problem also.
Fuel and Air lines from quality manufactures like as Motion Pro provide both clear, blue and reinforced fuel and air lines. You also must consider your intake manifold and that all lines are free and clear. You may also use larger lines to get it going. Along with these adding a Larger 95 Main Jet gets the added fuel needed. Intake manifolds are mainly for the 150 engine but will fit the 50cc also, you may have to modify the intake on the head to make it worth while. With 150s there are more jets sizes to choose from 95-150.
Quality Carbs from Keihin/Walboro and OKO, these carbs are much better than the chinese stock ones that come on most scooters and easily bolt right up. The OKO is a 20mm for 139QMB which is only 1mm difference but with the quality of this carb gives you the advantage over stock. Also 150 stock carbs from Walboro/Keihin also are much better than stock carbs. You may also upgrade to a 30mm or 32mm from OKO with jets also a choice for improvement. On a 150 adding a Keihin carb with a 130 jet adds great performance when doing upgrades.
Air Filters that are free flow from UNI and EMGO with great chrome looks and washable filters that last and get the right amount of air flow to the carb to keep up with a larger jet and more gas flow form better gas and air lines. This will help regardless of any other upgrades such as cylinder kits or exhaust but if you are doing one of these then by all means upgrade fuel and air. Some scooters just plain lack in these areas because of the quality of materials used from the start also knowing that these will crack and need replacing at some time.
The last problem area is the fuel valve or petcock valve which is vacuum actuated when the motor is turning over it pulls gas out of gas tank and into carb. These can be checked by unhooking gas line from carb and when you turn engine over or try to start a good flow should occur or its not working correctly. If you have a fuel valve NOT attached to gas tank we have the perfect upgrade with high flow high performance valve.
When fuel and air are suspect for a poor running scooter a simple upgrade with a jet and air filter and fuel valve will do the trick in most cases.
Electrical
With the right coil, cdi and spark plug with a good performing magneto your electrical system keeps a good spark firing to provide the fire needed to run engine.
Performance CDIs from MRP have provided no rev limit CDIs as well as Motori for the GY6 engines along with the standard Bando High Performance Coil .
There are several to choose from including the 9000 which has provided the best results and an adjustable MRP 150 CDI that gets the job done rather well for both scooters and go carts.
Spark plugs always play a role and should not be over looked. Make sure they are plugged in well and connecting wire and plug are doing the job same as fuel and air lines you must start with quality parts. New and well performing plugs always help and make a difference for starting gas mileage and performance over all. Use NGK C7HSA and NGK Iriduim CR7HIX for best performance.
There are some better magnetos coming out, at this point we have not found any with a good supply so we are limited to stock ones at this point. The stock mags are getting it done right now. NCY and a few others have offered some mags but we have not seen them yet. We do also carry the tool to remove magnetos with ease.
Transmission
The transmission is got to be my favorite next to exhaust for a workable upgrade and a way to slove a lot of problems of a slow un-powerful scooter.
Clutch
Variator
Roller Weights
Belt
Compression Spring
Clutch Springs
Best place to stat here is rear clutch or for fastest upgrade simply change roller weights to a lighter weight will increase take off plus hill climbing to a degree.
Once you go into trans I suggest change rear clutch and bell plus roller weights and belt to a Kevlar belt from Polini or Malossi plus MRP has a few out now also.
The best results we get on 139QMB is with clutch replacement with Dr Pulley 161301 doing the job nicely or the Prodigy which is most popular and the biggest bang for the money.
Adding a Dr Pulley clutch and bell to a 139QMB has got to be one of the best upgrades that can be done.
Same as for 150s but there are also MRP clutch with a MRP Chrome bell that does a nice job also when combines with a new compression spring some really nice power is gained.
Adding a Dr Pulley Clutch and Bell, Kevlar belt 9 or 10gram Slider weights is a killer upgrade for 150, add MRP High performance exhaust jet and air filter to keep going for even better performance.
As fas as variator go with the Prodigy or Dr Pulley when we have them was the best we found, some Polini and Malossi ones work also on 139QMB and for 150cc scooters the DR Pulley is by far the choice that gets results.
Performance variators have teflon ramp plates with greater angles to make pick up easier and quicker with better gear ratio for take off and climbing hills. With quality roller weights from DR Pulley and Polini you can even further tune your scooter for your needs. A 5gram Dr Pulley weight is best for 50cc with a 10 gram for 150cc perform better all around not giving up too much top end.
150cc Go Carts and Scooters really benifit from a clutch upgrade whether it be springs or as we suggest a high performance clutch from Dr Pulley and MRP. The power of the GY6 150cc engine lends itself with enough power to make a difference. Malossi and Polini each also have clutches and bells for GY6 engines just a little harder to find and test to getthe right ones.
Go Carts with GY6 150 engine perform well after a DR Pulley clutch upgrade with 10gram Dr Pulley sliders and new belt make hill climbing and trail rides that much more. Continue with a variator upgrade for top performance. You do have a choice in clutches, belts and variators to choose from with the Prodigy with its lower price still gets it done well when used with roller weights and belt.
Scooters using the GY6 150cc engine getting a clutch upgrade with get better performance in commuting in traffic and hill climbing and when combined with a roller weight upgrade with 9/10gram weights for a good average without taking away top end.
Engine
The engine whether 49cc or 147 cc can be upgraded with larger cylinders and pistons plus the head which should not be forgotten because when you add a larger piston and cylinder you will need larger valves to allow more air and fuel in and exhaust flow out. Now I do say do not forget but you do not have to add to make the cylinder kits work they will just not as good.
The GY6 50 has several choices of 47mm 70cc upgrade or 51mm 82cc upgrade which is by far the better of the two kits but both do a real good job of getting a slow four stroke scooter up to speeds of 50 plus. Real easy getting 45 as an average with going up hills no problem. As always an exhaust really helps because these pipes on the Chinese scooters are so restricted and also my favorite Prodigy Clutch plus Dr Pulley 5 gram roller weights along with Kevlar belt and you a scooter that gets done what ever you throw at it.
