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Yamaha F50 Service Manual

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    							62Y3A115-4
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    Symptom: Engine can be started, but does not remain on.
    Check the fuel system.
    Check the ignition system.
    Check the compression pressure of power unit.
    Is the vent 
    screw open?
    Water or resi-
    due?
    Good operat-
    ing condition?
    Kinks or fuel 
    leakage?
    Replace the pri-
    mary fuel pump.
    Check for water or residue in 
    the fuel filter.
    Open the fuel vent screw.
    Replace the respective parts.
    Clean the fuel system from the 
    fuel tank to the fuel filter.
    Check the fuel hose for kinks or 
    fuel leakage.
    Check the carbure-
    tors.
    No
    Yes
    Yes
    Yes
    Yes
    No
    No
    No
    Check the primary 
    pump operation.
    Check that the fuel vent screw of the fuel tank is open.
    Troubleshooting 
    						
    							POWRPower unit
    5-562Y3A11
    Is there air 
    intake?Replace the respective seals.
    Check the compression pres-
    sure of the combustion chamber.
    No
    Yes
    Check that there is no secondary air intake on the contact surfaces of 
    the intake manifold and crankcase.
    Check the ignition spark gap using the spark gap tester.
    Out of specifi-
    cation?
    Replace the spark plug.
    Check the ignition system out-
    put peak voltage.
    Yes
    No 
    						
    							62Y3A115-6
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    I
    Symptom: The engine idle speed is not steady, but increases or decreases.
    Check the carburetors.
    Check the air intake system.
    Check the ignition system.
    Replace the CDI unit.
    Check and disassemble the car-
    buretors, and then clean them if 
    necessary.
    Check the throttle cable opera-
    tion and lubricate it if necessary.
    Out of specifi-
    cation?
    Do the valves 
    close simul-
    taneously?
    Do the valves 
    close simul-
    taneously?
    Check the second-
    ary air intake on the 
    O-ring and manifold 
    plate, and the gas-
    kets of the vacuum 
    check bolts.
    Check the ignition timing.
    Yes
    No
    No
    Yes
    No
    Yes
    Check the operation of the car-
    buretor throttle valves by 
    removing the throttle cables and 
    link rods.
    Check the operation of the car-
    buretor throttle valves.
    Troubleshooting 
    						
    							POWRPower unit
    5-762Y3A11
    Symptom: Engine does not accelerate when the throttle is opened quickly.
    The engine turns off when the throttle is opened quickly.
    Acceleration is tardy and the engine is likely to stop at any moment.
    Check the carburetors.
    Check the ignition system.
    Check the compression pressure of power unit.
    Check the needle valve of the 
    carburetor for debris or wear.
    Adjust the throttle cable.
    Check each jet of the carburetor 
    for clogs or debris.
    Clean or replace the respective 
    parts.
    Debris or 
    wear?
    Check the ignition 
    system and the 
    compression pres-
    sure of the engine.
    Clogs or 
    debris?
    Yes
    No
    Yes
    Yes
    No
    No
    Check the throttle cable opera-
    tion.
    Clean the carburetor, or replace 
    respective parts.
    Do the carbu-
    retor throttle 
    valves close 
    simulta-
    neously? 
    						
    							62Y3A115-8
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    Symptom: Engine can run, but engine speed will not increase.
    Overheat warning indicator is on.
    Oil pressure warning indicator is on.
    Warning indicator is on and buzzer is sounding.
    Check the water cooling system.
    Check the lubricating system.
    Check the water inlet for clogs 
    or debris.
    Check the thermoswitch.
    Check that cooling water is dis-
    charged from the pilot water 
    outlet.
    Replace the thermostat.
    Replace the CDI unit.
    Replace the thermoswitch.
    Check the water 
    pump impeller.
    Check the water 
    passage.
    Clogs or 
    debris?
    Is water dis-
    charged?
    Good condi-
    tion?
    Good condi-
    tion?
    Good condi-
    tion?
    Clean the water inlet.
    Yes
    No
    No
    Yes
    Yes
    Yes
    No
    No
    Check the thermostat operation.
    Replace the impel-
    ler. No
    Yes
    Troubleshooting 
    						
    							POWRPower unit
    5-962Y3A11
    Check the oil pump for debris or 
    wear.
    Check the engine oil level.
    Check the oil pressure.
    Check the oil pressure switch.Clean or replace the respective 
    parts.
    At specified 
    level?
    Out of specifi-
    cation?
    Good condi-
    tion?
    Debris or 
    wear?Check the oil pas-
    sage.
    Yes
    No
    Yes
    No
    Yes
    Yes
    No
    No
    Add engine oil to the correct 
    level.
    Replace the oil pressure switch.
    Replace the CDI unit. 
    						
    							62Y3A115-10
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    Special service tools5
    Compression gauge
    YU-33223-1
    Flywheel magnet holder
    YB-06139
    Universal puller
    YB-06117
    Crankshaft holder
    YB-06562
    Valve spring compressor
    YM-01253Valve guide remover
    YM-01122
    Valve guide reamer
    YM-01196
    Valve seat cutter set
    YM-91043-C
    Drive shaft needle bearing depth stop
    YB-34473
    Oil filter wrench
    YU-38411
    For USA and Canada
    Special service tools 
    						
    							POWRPower unit
    5-1162Y3A11
    Piston ring compressor
    YU-33294
    Compression gauge
    90890-03160
    Flywheel holder
    90890-06522
    Flywheel puller
    90890-06521
    Crankshaft holder 18
    90890-06562Valve spring compressor
    90890-04019
    Valve spring compressor attachment
    90890-06320
    Valve guide remover/installer
    90890-06801
    Valve guide reamer
    90890-06804
    Valve seat cutter holder
    90890-06316
    For worldwide 
    						
    							62Y3A115-12
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    Valve seat cutter
    90890-06315, 90890-06323, 90890-06326, 
    90890-06328, 90890-06555
    Bearing outer race attachment
    90890-06626
    Oil filter wrench
    90890-01426
    Piston slider
    90890-06529
    Special service tools 
    						
    							POWRPower unit
    5-1362Y3A11
    Power unit5 
    						
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