Before taking anything apart, be sure to drain the fuel from both the gas tank and the carburetor’s float bowl. You’ll find the drain tube hanging off of the very bottom (driver’s side) of the carburetor. Most 125cc ?C 150cc GY6 carburetors have a valve immediately next to the drain tube that can be opened with a flat-blade screwdriver.
Other setups have the valve at the tip of the drain tube. If your carburetor is aftermarket came from a lower-price source, you might not have a valve or tube at all. Be careful opening the float bowl on one of those, as gas will spill if you’re not holding it upright.
1.Remove the carburetor from the engine by loosening the clamp on the intake inlet manifold. Flip it over and remove the four screws that fasten the float bowl.
2.Remove the float pin, push it through using a pointed tool.
3.Using a flat-blade screwdriver, remove both of the jets circled in the center. Spray carburetor cleaner through the three passages that are circled. The spray should dissolve and remove any blockages caused by old gasoline.
4.Look through both jets. You should see light coming from the end of each one. The most troublesome piece is the longer pilot jet which has a very narrow internal passage. Compressed air and chemicals might not work. In that case, use a single strand of copper from an electrical wire to clean out the blockage.
For carburetors that are severely gummed up we use compressed air @ 120psi to clean the passages. In some cases it may be necessary to let it soak overnight in carburetor dip.
Note: A little gas may spill out of the carburetor’s overflow tube when you flip it over to get to the float bowl.