Overheating; Engine; Cooling System; Fuel System - Yamaha XT660R Service Manual

EAS00855

OVERHEATING

ENGINE

Clogged coolant passages
• Cylinder head and piston
• Heavy carbon buildup
Engine oil
• Incorrect oil level
• Incorrect oil viscosity
• Inferior oil quality

COOLING SYSTEM

Coolant
• Low coolant level
Radiator
• Damaged or leaking radiator
• Faulty radiator cap
• Bent or damaged radiator fin
Water pump
• Damaged or faulty water pump
• Thermostat
• Thermostat stays closed
• Damaged hose
• Improperly connected hose
• Damaged pipe
• Improperly connected pipe
EAS00856

OVERCOOLING

COOLING SYSTEM
Thermostat
• Thermostat stays open
EAS00857

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
OVERHEATING/OVERCOOLING/
POOR BRAKING PERFORMANCE
9 - 4

FUEL SYSTEM

Throttle body
• Faulty throttle body
• Damaged or loose throttle body joint
Air filter
• Clogged air filter element

CHASSIS

Brake(s)
• Dragging brake

ELECTRICAL SYSTEMS

Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
Ignition system
• Faulty ECU
TRBL
SHTG