Zama Carburetor Technical Guide
How to Adjust a Zama Carburetor Step 1. Set the engine on a hard, flat surface. Locate the carburetor on the side of the engine, directly under the air Step 2. Gently turn the "L" and "H" adjustment screws clockwise until they seat with the flathead screwdriver. Step 3. Start the engine and allow. On most Zama carburetors to help find the correct adjustment there is a small L beside the Idle mixture screw and H beside the High speed mixture adjustment. Normal adjustment for 2 needle carburetors begins with the L needle. This adjustment. controls the fuel flow to the low speed or idle circuit. If the carburetor is too far out of adjustment to run, or has been disassembled, start with turning the L and .
How to adjust typical diaphragm carburetors. Ti most Zama carburetors to help find the correct adjustment there is a small L beside the Idle mixture screw and H beside the High speed mixture adjustment. Normal adjustment for 2 needle carburetors begins with the L needle. This adjustment. If the carburetor is too far out of adjustment to run, or has been disassembled, start with turning the L and H all the way in and then open 2 turns on each needle.
Adiust turn the TAS screw or idle speed adjustment in all the way. When turning any of these screws be careful not to over tighten, this craburetor cause damage to the carburetor.
Now you are ready to begin adjusting. Start the engine and allow it to warm up for a few minutes. Do not try to adjust the carburetor before the engine warms zmaa as settings change while the engine is warming up. Begin with the L needle, how to multiply decimals and fractions the needle in varburetor and listen to the engine as you do so.
The engine will speed up to a point then start slowing down again, the point of the highest speed is called optimum. This is at the most efficient point for the engine to run. When you find and set the engine to this point then adjust the TAS or idle speed android how to be root gt-p5210. This screw adjusts the idle speed, you should try to adjust it so the clutch is not engaged or ringing.
How to adjust zama carburetor when the clutch disengages the chain or string will stop moving. Some string trimmers do not have a clutch, so adjust these engines to a steady reliable speed. Once you have adjusted the idle speed it is necessary to recheck the L screw adjustment for the optimum point described above. It what is a service road be necessary to repeat these two how to adjust zama carburetor several times to get the engine to run correct.
The high speed adjustment procedure is similar to the L. Accelerate the engine to how to adjust zama carburetor speed and search for the optimum point as described for the L needle. The important part to remember about adjusting the L or H screw is not to let the engine drop much on the lean side of this point, screw in you want to find the highest speed when turning the needle.
However going too far past this point may result in engine damage. If your carburetor has no slots for a screwdriver, as in the picture below it is adjustable only with a special screwdriver available from the original equipment manufacturer. Zama is not offering any of these tools for sale. Skip to navigation Skip to content. Generic filters Hidden label.
Hidden label. Contact Us. How to adjust typical diaphragm carburetors On most Zama carburetors to help find the correct adjustment there is a small L beside the Idle mixture screw and H beside the High speed mixture adjustment. This adjustment controls the fuel flow to the low speed or idle circuit.
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Aug 03, · How to Adjust a Zama Carburetor. Zama carburetors are found on many different types of two-cycle lawn tools, from string trimmers to leaf blowers and edgers. How to adjust typical diaphragm carburetors On most Zama carburetors to help find the correct adjustment there is a small L beside the Idle mixture screw and H beside the High speed mixture adjustment. Normal adjustment for 2 needle carburetors begins with the L needle. This adjustment controls the fuel flow to the low speed or idle circuit. How to Adjust a Zama Carburetor. Set the engine on a hard, flat surface. Gently turn the "L" and "H" adjustment screws clockwise until they seat with the flathead screwdriver. Start the engine and allow to run for two to three minutes until the engine is at the operating temperature. Click to see full answer.
The fuel pump on a diaphragm carburetor uses the vacuum and pressure pulse from the engines crankcase to move a diaphragm up and down. The pulse travels from the crankcase through a drilled passage or a hose to the carburetor. As the diaphragm moves down and compresses the area in the pump chamber the fuel is forced through.
It is important to make sure the passage from the engine crankcase to the pump diaphragm is clear and not restricted in any way in order for the pump to operate properly. The purpose of the metering system is to control fuel flow. The main advantage of this system is that it is not affected by the orientation of the engine. The components of the fuel metering system consist of an inlet needle, metering lever, metering spring and metering diaphragm.
The pressure of the metering spring against the metering lever holds the inlet needle against its seat and prevents fuel from entering the metering chamber. The metering diaphragm is made of a flexible convoluted material to allow for greater movement.
As the engine runs, fuel is being drawn from the metering chamber in the carburetor. This causes the metering diaphragm to move up and contact the metering lever.
The pressure of the metering diaphragm against the lever over rides the spring pressure on the inlet needle. The fuel pressure from the pump is then great. A venturi is a constriction of the inside diameter of a tube. The Venturi is used to produce low pressure inside the bore of the carburetor.
The low pressure pulls fuel into the bore from the metering chamber where it mixes with the air and is drawn into the. When the bulb is depressed the outlet check valve is forced open and the air and fuel in the bulb passes through the outlet check valve and into the.
The vacuum from the expanding bulb draws fuel through the inlet check valve from. The vacuum in the metering chamber draws in on the metering diaphragm, and lifts the inlet needle. The open inlet needle causes the vacuum created by the primer to draw fuel from the tank, through the pump, into the metering chamber and up to the primer bulb. To prevent air from entering the metering chamber during primer operation there is a one-way check valve in the idle circuit and main nozzle.
Every time the primer bulb is depressed this process is repeated causing any old fuel or air that was in the carburetor to be displaced by fresh fuel from the tank. The fresh fuel in the carburetor makes the engine easier to start. Note that once the metering chamber has been filled with fresh fuel continuing to push on the primer bulb will not help improve the starting of the engine.
To start a cold engine the fuel and air mixture entering the engine must be rich. Closing or choking the air inlet of the carburetor using a choke valve accomplishes this. The choke valve allows very little air to enter, causing the engine vacuum to be concentrated inside the venturi of the carburetor. The high vacuum draws fuel from the high and low speed fuel circuits creating the very rich fuel and air mixture that is needed to start a cold engine. The full-choke operation is used to get the engine to fire and start.
In most cases the fuel air mixture is too rich to allow the engine to run for a long time before it dies. The engine is re-started and will continue to run in a rich condition.
After the engine has sufficiently warmed up in the half choke-position the choke valve can be moved to the full open position. At idle, fuel is delivered to the engine through the idle or low speed circuit. This circuit usually consist of two or three holes located along the throttle bore of the carburetor.
The throttle valve is slightly open allowing a small amount of air to pass through to the engine. This creates a low pressure vacuum on the engine side of the throttle valve and atmospheric pressure on the inlet other side of the valve. Air enters the secondary holes on the atmospheric side of the throttle valve and mixes with the fuel in the idle pocket creating an emulsified air fuel mixture.
The low pressure draws the fuel and air mixture through the first idle hole into the engine. As the fuel and air mixture is drawn out of idle pocket it creates low pressure in the metering chamber. Atmospheric pressure pushes the metering diaphragm against the metering lever. This releases the spring pressure applied to the inlet needle and allows fuel to flow into the metering chamber.
The main nozzle check valve is another important component of the idle circuit. This one way check valve located in the main nozzle is under atmospheric pressure at idle. Without it air would flow from the main nozzle into the metering chamber.
This will cause an air leak in the metering chamber and there would be no drop in pressure. The diaphragm will not move and the engine will die lean when idling. This check valve also serves the same function during the priming operation. During part throttle operation or acceleration the throttle valve is opened to allow more air to the engine.
The secondary idle holes are now on the vacuum side of the throttle valve and fuel is drawn. The increased airflow causes vacuum to be applied to the main nozzle. This allows fuel pressure from the metering chamber to overcome atmospheric pressure on the check valve and it begins to flow fuel to the engine.
The pressure drop from the venturi increases fuel flow from the main nozzle. Fuel from the main nozzle and idle circuit mixes with the air, entering the combustion chamber and satisfying the.
This section describes the procedure recommended to properly diagnose a Zama diaphragm carburetor problem on a two-cycle engine. If you have an engine performance problem and suspect the carburetor the first thing that must be done is to confirm that you actually have a carburetor problem. Above is a trouble-shooting guide that can help you diagnose engine problems that can often be mistaken for the carburetor.
We will assume you have confirmed the following items and inspected all the possible faults as specified in chart 1. After ruling out any engine related performance problems use chart 2 to help determine the fault for the carburetors malfunction. If the diagnoses result in action that involves repair of the carburetor then follow the disassembly and service instructions on the subsequent pages. Inspect each screw for damage, especially the needle points which should have no deformation of the.
A damaged needle or seat will result in a very sensitive needle. The needles will be difficult to adjust. If the carburetor is equipped with a plastic metering disk, remove it carefully. The disk must be smooth and free from cracks or chipped edges.
The center tip that fits into the metering lever hole must be secure. Inspect the metering lever. It should not be worn where it contacts the inlet needle valve and metering. Under the extreme conditions of a clogged idle port and channel, it may be necessary to remove the welch plug.
Do this operation very carefully. 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. Just below the welch plug there is a thin casting wall where the idle and secondary holes are located. Punching through this area will ruin the carburetor body casting.
Let the punch just pierce the welch plug, then carefully pry the welch plug out of the body casting. If the carburetor is equipped with the plastic filling in the idle chamber, it will be unusable when the welch plug is removed.
So, replace the plastic filling. Note: It is often un-necessary to remove the welch plug. Test for plugged progression holes by spraying carb cleaner into the L needle hole.
If cleaner sprays out the progression holes there is no need to remove the welch plug. Test the main nozzle by blowing air by mouth through the H needle feed hole with a small hose.
With the needle open 2 turns open air should flow through, but you should not be able to suck air back. If the carburetor is equipped with a pressed in nozzle assembly, do not attempt to remove it unless you are certain it is malfunctioning. If it is necessary to remove, carefully press it out with steel rod or punch. If the carburetor is equipped with a screw in nozzle assembly, remove it in the same manner as a normal. If the carburetor is equipped with a strainer and C-ring type, remove main welch plug, then remove C-ring.
Clean the carburetor body. Channels can be cleaned by blowing through the idle and main adjusting orifices with spray carburetor cleaner.
Do not soak in dip tank type cleaner. Do not use wires or drills to clean orifices. Inspect the operation of the throttle valve and lever. Replace all worn parts and make sure that all parts are clean before they are reassembled into carburetor. If nozzle assembly is a pressed in type, put a light oil film on the outside of the nozzle check valve cage. Carefully press the nozzle into the carburetor body until it is just flush with the metering chamber.
If the carburetor is a strainer and C-ring type, install the strainer and C-ring. Lay the main welch plug into. Lay the welch plug into the cavity. If the welch plug is circle shape, press it firmly with a flat end punch to expand it tightly against the sides of the cavity. If the welch plug is oblong shape, press it firmly with oblong punch. Press it firmly with oblong punch.
It is best to use sealer for sealing around the welch plug.