Chinese Scooter Carb Main Jet upgrade

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The process for changing the main jet size is pretty simple. First remove the carburetor. To do this you'll probably need to take some parts off the scooter, such as the underseat storage container and possibly some body panels. Every scooter will be different. Disconnect the fuel line and vacuum lines, disconnect the auto enricher (choke), disconnect the throttle cable, disconnect the air intake hose and disconnect the inlet manifold. At this point you should, be able to wiggle the carburetor out of the scooter.

At the bottom of most carburetors you'll find the float chamber, usually secured to the carburetor body by four screws. Remove these screws and the float chamber should separate from the body. If you haven't drained it, it will be full of gas, so be careful.

Scooter Carburetor Main Jet
On most carburetors, the main jet is the one which sticks out more. The jet itself is actually just the top part of the brass tube which sticks up out of the aluminum carburetor body . The lower part is the atomizer and it can stay in the carburetor body. Only the main jet need to be changed. Be sure to use the right sized screwdriver to remove it. Brass is quite soft and you don't want to damage the screw slot. So unscrew the main jet and replace it with the new one. Screw it in tight, but you don't need to use a lot of force. Just make sure it's not loose. That's it. You've now replaced the main jet in your carburetor!

Altitude can play an issue in scooter performance. When you are dealing with elevation you will want to rejet to prevent your engine from siezing and requiring a rebuild. You will loose about 3% in power for every 1000' in elevation. At 4000' feet you will have lost about 12% of your power output. You will want to go down one (1) jet size for every 1750' to 2000' you go up in elevation. When the air is colder it requires bigger jets because cold air is more dense. If it is 50 degrees colder you would increase your jet size at least one step up. If you don't, your engine may sieze on you.

This video is perfect for chinese scooter like gy6, lance, taotao and more