11/20/2023 0 Comments Zama carburetor airflow system![]() Inlet check valve you should not be able to suck air back through it. Make sure the actuating system is functioning. Check the carb mount and gaskets to make sure no sealer or a mis-aligned gasket is blocking the pulse hole. Make sure the crankcase pulse passages are open. If running the engine does not fix the system then proceed with the diagnosis. Occasionally the small passages in the starting circuit become clogged by small drops of oil or trash and running the engine will clear these obstructions. If the engine accelerates when the system is engaged and then gradually slows down and dies, the system is working. While running the engine engage the start system. If the rest of the engine and carburetor operates properly, but the Simple Start pump is not delivering fuel, and easy initial check can be done. The Simple Start system is calibrated to work with the properly adjusted, properly operating carburetor. Do this by starting the engine either by choking it with your hand or priming it with some fuel through the carburetor throat. If Simple Start is left on, the engine will eventually get too rich and die.įirst make sure the rest of the carburetor functions properly. As the engine warms up it does not need this extra fuel so it begins running richer and richer and begins to slow down. ![]() This can lead to confusion if you take both needles out and do not identify them.Servicing Simple Start® System CarburetorsĪs the Start Pump receives the crankcase pressure and vacuum pulses, it begins to suck fuel from the metering chamber into the start pump, and spray it out of the injector hole in the throttle bore. The H needle on some carburetors is now the same thread size as the L needle. On many of the new emissions carburetors we reduced the sensitivity of the H needle to make it easier to precisely set the carburetor mixture. So while the limit caps have made it more difficult to preset the carburetor and to remove the needles, they have also made it less likely that the needles will get far out of adjustment, or that they will even need to be removed for cleaning. This is because with the limit caps on it becomes much more difficult to remove the needles for cleaning. Another thing we have tried to do is increase the clearance between the needle and the seat to make sure less debris collects there. So while we still try to have a preset of 1 turn, many needles fall between one and two turns open. When we had to begin using limiter caps we also decreased the needle sensitivity in many cases. All three diaphragms found in the Zama carburetor kits offer resistance to alcohol fuels.īefore carburetor L and H needles had limit caps the standard pre-set on the L and H needles was one turn open. You must use the black buna diaphragm also found in the kits. If your carburetor does not have a machined fuel pump surface you cannot use either the tan or the clear diaphragm. The tan Teflon coated pump diaphragm has been superseded by the clear mylar diaphragm. It should hold this pressure for a minimum of 15 seconds. Rather than pressurizing the carburetor to pop-off, Zama recommends that the carburetor should be pressurized at the fuel fitting to 10 p.s.i. In fact checking pop-off pressure can often damage the carburetor by stretching the fuel pump diaphragm and breaking the seal of the fuel pump gasket. A lot of emphasis has been placed on carburetor pop-off pressures when in reality they are not an important issue to the service professional.
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