Troubleshooting; Starting Failure/Hard Starting; Engine; Fuel System - Yamaha YJ50RN Service Manual

STARTING FAILURE/HARD STARTING

EAS00845
NOTE:
@
The following guide for troubleshooting does not cover all the possible causes of trouble. It should
be helpful, however, as a guide to basic troubleshooting. Refer to the relative procedure in this man-
ual for checks, adjustments, and replacement of parts.
STARTING FAILURE/HARD STARTING

ENGINE

Cylinder and cylinder head
• Loose spark plug
• Loose cylinder head or cylinder
• Damaged cylinder head gasket
• Damaged cylinder gasket
• Worn or damaged cylinder
Piston and piston ring(s)
• Improperly installed piston ring
• Damaged, worn or fatigued piston ring
• Seized piston ring
• Seized or damaged piston
Air filter
• Improperly installed air filter
• Clogged air filter element
Crankcase and crankshaft
• Improperly assembled crankcase
• Seized crankshaft

FUEL SYSTEM

Fuel tank
• Empty fuel tank
• Clogged fuel tank cap breather hole
• Deteriorated or contaminated fuel
• Clogged or damaged fuel hose
Carburetor
• Deteriorated or contaminated fuel
• Clogged pilot jet
• Clogged pilot air passage
• Sucked-in air
• Damaged float
• Worn needle valve
• Improperly installed needle valve seat
• Incorrect fuel level
• Improperly adjusted pilot air screw
• Improperly installed pilot jet
• Clogged starter jet
• Clogged emulsion tube

TROUBLESHOOTING

Autochoke unit
• Faulty starter plunger
• Faulty ignitor unit

ELECTRICAL SYSTEMS

Battery
• Improperly charged battery
• Faulty battery
Fuse
• Blown, damaged or incorrect fuse
• Improperly installed fuse
Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
• Faulty spark plug cap
Ignition coil
• Broken or shorted primary or secondary coil
• Faulty spark plug lead
• Cracked or broken ignition coil body
Ignition system
• Faulty ignitor unit
• Faulty pickup coil
• Broken generator rotor woodruff key
Switches and wiring
• Faulty main switch
• Faulty engine stop switch
• Broken or shorted wiring
• Faulty front, rear or both brake switches
• Faulty start switch
• Improperly grounded circuit
• Loose connections
Starting system
• Faulty starter motor
• Faulty starter relay
• Faulty starter clutch
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TRBL
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