![]() After completion, I checked the fuel tank and decided to pump the prime bulb and see what happened, it started after a few pulls and continued to use the saw finishing the last cut and several more on the log where it quit two months ago. So this wasn't the first time and I thought that it would take 30-60 minutes, but at 60 minutes the last part to replace was the start lever which includes an electrical connector which is a prickly through a hole to a flat spring that is fussy to align, and an apparent trick sequence. The throttle is connected, usually through a cable or a mechanical linkage of rods and joints.įuel is introduced into the air stream through small holes at the narrowest part of the Venturi and at other places where pressure will be lowered when not running on full throttle.Īnything with the fuel system requires removing the carburetor on a Husqvarna designed saw. This valve controls the flow of air through the carburetor throat and thus the quantity of air/fuel mixture the system will deliver, thereby regulating engine power and speed. The pipe is in the form of a Venturi: it narrows in section and then widens again, causing the airflow to increase in speed in the narrowest part.īelow the Venturi is a butterfly valve called the throttle valve - a rotating disc that can be turned end-on to the airflow, so as to hardly restrict the flow at all, or can be rotated so that it (almost) completely blocks the flow of air. Zama is not offering any of these tools for sale.A carburetor basically consists of an open pipe through which the air passes into the inlet manifold of the engine. 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. As with the L adjustment the H needle may be richened a little, but no more then ¼ turn from optimum point. ![]() However going too far past this point may result in engine damage. ![]() 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. The high speed adjustment procedure is similar to the L.Īccelerate the engine to full speed and search for the optimum point as described for the L needle. The L screw may be opened 1/8 to 1/4 turn from this optimum point to help the engine to accelerate well to full throttle. It may be necessary to repeat these two adjustments several times to get the engine to run correct. Once you have adjusted the idle speed it is necessary to recheck the L screw adjustment for the optimum point described above. Some string trimmers do not have a clutch, so adjust these engines to a steady reliable speed. ![]() Note: when the clutch disengages the chain or string will stop moving. This screw adjusts the idle speed, you should try to adjust it so the clutch is not engaged or ringing. When you find and set the engine to this point then adjust the TAS or idle speed screw. This is at the most efficient point for the engine to run. The engine will speed up to a point then start slowing down again, the point of the highest speed is called optimum. Begin with the L needle, turn the needle in clockwise and listen to the engine as you do so. Do not try to adjust the carburetor before the engine warms up as settings change while the engine is warming up. Start the engine and allow it to warm up for a few minutes.
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