Guide to GY6 150cc Carbs
This is the Small Fast Things definitive guide to GY6 150cc carburetors both stock and aftermarket. Use this only as reference when shopping for a carb for your Ruckus GY6 swap or GY6 scooter. This does not serve as a howto nor is it a replacement for testing and tuning. Proper performance gains can only be achieved with proper carb jetting and adjustment and is not a "one size fits all" solution.
The popular GY6 150cc motor that is swapped into Honda Ruckuses and found in many common Chinese scooters is a carburetor operated engine. It comes standard with a CVK style carburetor usually in a 24mm or 26mm intake size. It is a great carb that is inexpensive, easy to maintain, and very forgiving in a variety of different climate conditions. If you have any experience with old carbureted cars, motorcycles, etc you will understand how much weather can affect how a carburetor runs. This is the case with all carbs no matter what size and style you run on your GY6. The stock CVK style carb features a diaphragm needle valve that rises and lowers depending on vacuum pressure and allows fuel to enter the engine automatically. It is a self regulating system which is what makes the stock CVK so dependable and flexible. The stock GY6 can be tuned by changing the main or pilot jets and also via adjustment of the air/fuel screw. Lastly, it has an auto fuel enricher for easy starting. In all, it is a great carb to use if you want a low maintenance carb that has a few auto features for ease of use.
A Skinny GY6 Ruckus Swap featuring the SFT Skinny GY6 Mount with correct stock CVK carb orientation.
If you are thinking about upgrading your GY6 150cc carb, the only real aftermarket solution is a Flat or Round Style Slide Carb. The main difference between these styles carbs and the stock carb is the main slide. As mentioned above, the stock CVK carb has a diaphragm needle valve slide that meters or lets fuel into the motor based on engine vacuum at different RPMs or operating loads. In a flat or round style slide carb, the fuel metering is all mechanically done via main slide that is directly connected to the throttle cable. The instant you twist the throttle, the valve opens and starts letting fuel into the motor. This features is great because it offers excellent throttle response and power control. The downside to these carbs are they require more tuning and are more susceptible to weather changes. But flat or round slide carbs tend to be less complicated than CVK style carbs so they are easy to work on and tune.
A popular and inexpensive flat slide carb and a Small Fast Things favorite is the OKO brand of flat slide carbs. They come in a raw finish and a more sporty looking black in many different sizes from 24mm all the way up to 30mm. These are great carbs for big bore builds and are very easy to work with. Here's a freebie...we personally run a 30mm OKO carb with 120 main jet and a 38 pilot on a shop built 171cc GY6 motor.