Yamaha MT-03 - Service manual > Troubleshooting

General information

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 manual for checks, adjustments, and replacement of parts.

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
• Clogged fuel tank drain hose
• Deteriorated or contaminated fuel

2. Fuel pump

• Faulty fuel pump
• Faulty relay unit

3. Throttle body

• Deteriorated or contaminated fuel
•  Sucked-in air

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 A.C. magneto rotor woodruff key

6. Switches and wiring

• Faulty main switch
• Faulty engine stop switch
• Broken or shorted wiring
• Faulty neutral switch
• Faulty start switch
• Faulty sidestand switch
• Faulty clutch switch
• Improperly grounded circuit
• Loose connections

7. Starting system

• Faulty starter motor
• Faulty starter relay
• Faulty starting circuit cut-off relay
•  Faulty starter clutch

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 (throttle stop screw)
• Improper throttle cable free play
• Flooded throttle body
• Faulty air induction system

Electrical system

1. Battery

• Discharged battery
• Faulty battery

2. 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

3. Ignition coil

• Broken or shorted primary or secondary coils
• Faulty spark plug lead
• Cracked or broken ignition coil

4. Ignition system

• Faulty ECU
• Faulty crankshaft position sensor
• Broken A.C. magneto rotor woodruff key

Poor medium-and-high-speed performance

Engine

1. Air filter

• Clogged air filter element

Fuel system

1. Fuel pump

• Faulty fuel pump

Faulty gear shifting

Shifting is difficult

Refer to "Clutch drags".

SHIFT PEDAL DOES NOT MOVE

Shift shaft

• Improperly adjusted shift rod
• Bent shift shaft

Shift drum and shift forks

• Foreign object in a shift drum groove
• Seized shift fork
• Bent shift fork guide bar

Transmission

• Seized transmission gear
• Foreign object between transmission gears
• Improperly assembled transmission

JUMPS OUT OF GEAR

Shift shaft

• Incorrect shift pedal position
• Improperly returned stopper lever

Shift forks

• Worn shift fork

Shift drum

• Incorrect axial play
• Worn shift drum groove

Transmission

• Worn gear dog

Faulty clutch

Clutch slips

1. Clutch

• Improperly assembled clutch
• Improperly adjusted clutch cable
• Loose or fatigued clutch spring
• Worn friction plate
• Worn clutch plate

2. Engine oil

• Incorrect oil level
• Incorrect oil viscosity (low)
• Deteriorated oil

Clutch drags

1. Clutch

• Unevenly tensioned clutch springs
• Warped pressure plate
• Bent clutch plate
• Swollen friction plate
• Bent clutch push rod
• Damaged clutch boss
• Burnt primary driven gear bushing
• Damaged clutch release cylinder
• Match marks not aligned

2. Engine oil

• Incorrect oil level
• Incorrect oil viscosity (high)
• Deteriorated oil

Overheating

Engine

1. Clogged coolant passages

2. Cylinder head and piston

• Heavy carbon buildup

3. Engine oil

• Incorrect oil level
• Incorrect oil viscosity
• Inferior oil quality

Cooling system

1. Coolant

• Low coolant level

2. Radiator

• Damaged or leaking radiator
• Faulty radiator cap
• Bent or damaged radiator fin

3. Water pump

•  Damaged or faulty water pump
• Thermostat
• Thermostat stays closed
• Damaged hose
• Improperly connected hose
• Damaged pipe
• Improperly connected pipe

Fuel system

1. Throttle body

• Faulty throttle body
• Damaged or loose throttle body joint

2. Air filter

• Clogged air filter element

Chassis

1. Brake(s)

• Dragging brake

Electrical system

1. Spark plug

• Incorrect spark plug gap
• Incorrect spark plug heat range

2. Ignition system

• Faulty ECU

Overcooling

Cooling system

1. Thermostat

• Thermostat stays open

Poor braking performance

• Worn brake pad
• Worn brake disc
• Air in hydraulic brake system
• Leaking brake fluid
• Faulty brake caliper seal
• Loose union bolt
• Damaged brake hose
• Oil or grease on the brake disc
• Oil or grease on the brake pad
• Incorrect brake fluid level

Faulty front fork legs

Leaking oil

• Bent, damaged or rusty inner tube
• Cracked or damaged outer tube
• Improperly installed oil seal
• Damaged oil seal lip
• Incorrect oil level (high)
• Loose damper rod assembly bolt
• Damaged damper rod assembly bolt copper washer
• Cracked or damaged cap bolt O-ring

Malfunction

• Bent or damaged inner tube
• Bent or damaged outer tube
• Damaged fork spring
• Worn or damaged outer tube bushing
• Bent or damaged damper rod
• Incorrect oil viscosity
• Incorrect oil level

Unstable handling

1. Handlebar

• Bent or improperly installed handlebar

2. Steering head components

• Improperly installed upper bracket
• Improperly installed lower bracket (improperly tightened ring nut)
• Bent steering stem
• Damaged ball bearing or bearing race

3. Front fork leg(s)

• Uneven oil levels (both front fork legs)
• Unevenly tensioned fork spring (both front fork legs)
• Broken fork spring
• Bent or damaged inner tube
• Bent or damaged outer tube

4. Swingarm

• Worn bearing or bushing
• Bent or damaged swingarm

5. Rear shock absorber assembly

• Faulty rear shock absorber spring
• Leaking oil or gas

6. Tire(s)

• Uneven tire pressures (front and rear)
• Incorrect tire pressure
• Uneven tire wear

7. Wheel(s)

• Incorrect wheel balance
• Deformed cast wheel
• Damaged wheel bearing
• Bent or loose wheel axle
• Excessive wheel runout

8. Frame

• Bent frame
• Damaged steering head pipe
• Improperly installed bearing race

Faulty lighting or signaling system

Headlight does not come on

• Wrong headlight bulb
• Too many electrical accessories
• Hard charging
• Incorrect connection
• Improperly grounded circuit
• Poor contacts (main or light switch)
• Burnt-out headlight bulb
• Faulty headlight relay
• Faulty ECU

Headlight bulb burnt out

• Wrong headlight bulb
• Faulty battery
• Faulty rectifier/regulator
• Improperly grounded circuit
• Faulty main switch
• Headlight bulb life expired

Tail/brake light does not come on

• Wrong tail/brake light bulb
• Too many electrical accessories
• Incorrect connection
• Burnt-out tail/brake light bulb

Tail/brake light bulb burnt out

• Wrong tail/brake light bulb
• Faulty battery
• Tail/brake light bulb life expired

Turn signal does not come on

• Faulty turn signal switch
• Faulty turn signal/hazard relay
• Burnt-out turn signal bulb
• Incorrect connection
• Damaged or faulty wire harness
• Improperly grounded circuit
• Faulty battery
• Blown, damaged or incorrect fuse

Turn signal flashes slowly

• Faulty turn signal/hazard relay
• Faulty main switch
• Faulty turn signal switch
• Incorrect turn signal bulb

Turn signal remains lit

• Faulty turn signal/hazard relay
• Burnt-out turn signal bulb

Turn signal flashes quickly

• Incorrect turn signal bulb
• Faulty turn signal/hazard relay
• Burnt-out turn signal bulb

Horn does not sound

• Improperly adjusted horn
• Damaged or faulty horn
• Faulty main switch
• Faulty horn switch
• Faulty battery
• Blown, damaged or incorrect fuse
• Faulty wire harness

WIRING DIAGRAM

MT-03 2006

1. Crankshaft position sensor
2.  A.C. magneto
3. Neutral switch
4. Main switch
5. Rectifier/regulator
6. Wire plus lead
7. Battery
8. Main fuse
9. Starter relay
10. Starter motor
11.  Wire minus lead
12. Relay unit
13. Starting circuit cut-off relay
14. Fuel injection system relay
15. Fuel injection diagnostic tool
16. Ignition coil
17. Spark plug
18. Fuel injector
19. Air induction system solenoid
20. Intake air temperature sensor
21. Coolant temperature sensor
22. .ECU
23. Speed sensor
24. Throttle position sensor
25. Intake air pressure sensor
26. Lean angle cut-off switch
27. Multi-function meter unit
28. Neutral indicator light
29. Multi-function meter
30. Fuel level warning light
31. Turn signal indicator light
32. High beam indicator light
33. Coolant temperature warning light
34. Immobilizer system indicator light
35. Multi-function meter light
36. Engine trouble warning light
37. Fuel pump
38. Sidestand switch
39. Front brake light switch
40. Right handlebar switch
41. Engine stop switch
42. Start switch
43. Turn signal/hazard relay
44. Headlight relay
45. Clutch switch
46. Hazard switch
47. Turn signal switch
48. Dimmer switch
49. Pass switch
50. Horn switch
51. Left handlebar switch
52. Rear turn signal light (right)
53. Front turn signal light (right)
54. Front turn signal light (left)
55. Rear turn signal light (left)
56. Headlight
57. Horn
58. Tail/brake light
59. Auxiliary light
60. License light
61. Rear brake light switch
62. Radiator fan motor
63. Radiator fan motor relay
64. Parking lighting fuse
65. Headlight fuse
66. Signaling system fuse
67. Ignition fuse
68. Radiator fan motor fuse
69. Backup fuse (immobilizer unit, multi-function meter unit)
70. Fuel injection system fuse
71. Anti-theft alarm (optional)
72. Immobilizer unit

Color code

MT-03 2006 WIRING DIAGRAM

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