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Yamaha FZ 25 2021 - General Troubleshooting Guide; Starting Failures Troubleshooting; Incorrect Engine Idling Speed Issues

Yamaha FZ 25 2021
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7-1
TRBL
SHTG
TROUBLESHOOTING
TROUBLESHOOTING
EAS28450
TROUBLESHOOTING
EAS28460
GENERAL INFORMATION
The following guide for troubleshooting does not
cover
all the possible causes of trouble. It should
be helpful, however, as a guide to basic trouble-
shooting. Refer to the relative procedure in this
manual for checks, adjustments, and replace-
ment of parts.
EAS28470
STARTING FAILURES
Engine
1. Cylinder and cylinder head
Loose spark plug
Loose cylinder head or cylinder
Damaged cylinder head gasket
Damaged cylinder gasket
Worn or damaged cylinder
Incorrect valve clearance
Improperly sealed valve
Incorrect valve-to-valve-seat contact
Incorrect valve timing
Faulty valve spring
Seized valve
2. Piston and piston ring(s)
Improperly installed piston ring
Damaged, worn or fatigued piston ring
Seized piston ring
Seized or damaged piston
3. Air filter
Improperly installed air filter
Clogged air filter element
4. Crankcase and crankshaft
Improperly assembled crankcase
Seized crankshaft
Fuel system
1. Fuel tank
Empty fuel tank
Deteriorated or contaminated fuel
Clogged fuel tank cap breather hole
Clogged or damaged fuel hose
2. Fuel pump
Faulty fuel pump
Clogged fuel pump filter
3. Throttle body
Deteriorated or contaminated fuel
Sucked-in air
4. Canister
Hose clogged
Hose band / twisted
Electrical system
1. Battery
Discharged battery
Faulty battery
2. Fuse(s)
Blown, damaged or incorrect fuse
Improperly installed fuse
3. 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
4. Ignition coil
Cracked or broken ignition coil body
Broken or shorted primary or secondary coils
Faulty spark plug lead
5. Ignition system
Faulty ECU
Faulty crankshaft position sensor
Broken AC magneto rotor woodruff key
6. Switches and wiring
Faulty main switch
Faulty engine stop switch
Broken or shorted wiring
Faulty neutral switch
Faulty front, rear or both brake light switches
Faulty start switch
Faulty sidestand switch
Faulty clutch switch
Improperly grounded circuit
Loose connections
7. Starting system
Faulty starter motor
Faulty starter relay
Faulty starter clutch
EAS28490
INCORRECT ENGINE IDLING SPEED
Engine
1. Cylinder and cylinder head
Incorrect valve clearance
Damaged valve train components
2. Air filter
Clogged air filter element
Fuel system
1. Throttle body
Damaged or loose throttle body joint
Improperly adjusted engine idling speed (idle
adjusting screw)
Improper throttle cable free play
Flooded throttle body
Faulty air induction system
B9X-F8197-E0.book Page 1 Thursday, July 16, 2020 2:28 PM

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