![]() If the carburetor is equipped with the priming pump, do not attempt to remove the welch plug unless you are certain the check valve in the idle chamber is malfunctioning. Under the extreme conditions of a clogged idle port and channel, it may be necessary to remove the welch plug. The tip should not be deformed where it contacts the seat. It should not be worn where it contacts the inlet needle valve and metering disk. Remove metering lever, pin, metering lever spring and inlet needle valve. The following instructions apply to all models. The center tip that fits into the metering lever hole must be secure and not broken or worn. ![]() The disk must be smooth and free from cracks or chipped edges. If the carburetor is equipped with a plastic metering disk, remove it carefully. Inspect the metering diaphragm for dirt and foreign matter. If the metering diaphragm is hooked type, remove it,īeing careful to unhook it from the metering lever. Remove screws and metering chamber cover or primer body. Inspect pump diaphragm, replace if diaphragm shows any signs of wear, wrinkles or tears. Remove the pump gasket and pump diaphragm. Remove pump cover screws and pump cover or primer body. FOR ALL OTHER TYPES: C1U, C1Q/M, C2, C3, C3A/M Remove metering diaphragm and metering chamber gasket. Inspect pump diaphragm, replace if diaphragm shows any signs of wear or curling. Remove the pump diaphragm and pump gasket. Remember that the L needle is always longer. Note: On dual needle carburetors the L and H needle are not interchangeable. The needles will be difficult to adjust and the carburetor will always run too rich or too lean. Inspect each screw for damage, especially the needle points which should have no deformation of the tapered surfaces.Ī damaged needle or seat will result in a very sensitive needle. ZAMA CUBE CARBURETOR DISASSEMBLY AND SERVICE MIXTURE SCREWS If you then open the choke plate the engine will start running normally.The Zama model number is stamped on the body of the carburetor. Usually this very rich mixture will allow the engine to fire once or twice, or to run very slowly. If the throttle is wide open and the venturi is covered, the engine's vacuum draws a lot of fuel through the main jet and the idle jet (since the end of the carb's tube is completely covered, all of the engine's vacuum goes into pulling fuel through the jets). When activated, the choke plate completely covers the venturi see this video of the choke plate to see it in action). ![]() It is also cold, so it needs a very rich mixture to start. When the engine is cold and you try to start it with the pull cord, the engine is running at an extremely low RPM. When you adjust them you are directly controlling how much fuel flows through the idle jet and the main jet. By turning them you allow more or less fuel to flow past the needle. ![]() The other screw of the pair seen in photo 1 is labeled "Lo" and it controls the amount of fuel that flows through the idle jet.īoth the Hi and Lo screws are simply needle valves. If a tiny hole is drilled into the side of the carb's tube just behind the throttle plate, fuel can be drawn into the tube by the throttle vacuum. However, on the back side of the throttle plate there is a lot of vacuum (because the throttle plate is restricting the airflow). There is not really enough air flowing through the venturi to create a vacuum. When the engine is idling, the throttle plate is nearly closed (the position of the throttle plate in the photos is the idle position).
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