2001-2002 Yamaha 50HP F50Z/T50Z Ouboard 4-stroke engines service manual, Page 13Get this manual
Features and benefits Technical tips Technical tips Carburetor
Starting system (Prime Start) To facilitate the starting of cold engine, an air-fuel mixture that is richer than normal is requiredFor this reason, the Prime Start system has been adopted in the F50F50A, T50FT50B, FT50CIn the Prime Start system, the thermo heater plunger is in position that fully opens the fuel enrichment valve while the engine is being startedThus, fuel enrichment is achieved during the starting of the engine, and continues while the engine is being warmed upOnce the engine starts, current flows from the lighting coil of the to the thermo heater, allowing the wax in the Prime Start unit to expandThe expanded wax moves the thermo heater plunger in the direction to close the enrichment valveAs result, the volume of fuel that passes through the fuel enrichment valve decreasesA few minutes after the engine has started, the thermo heater plunger completely closes the fuel enrichment valve, thus ending the fuel enrichment by the Prime Start system