Troubleshooting; Starting Failures - Yamaha YBR250 2007 Service Manual

TROUBLESHOOTING

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
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
Piston and piston rings
• 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
STARTING FAILURES
FUEL SYSTEM
Fuel tank
• Empty fuel tank
• Clogged fuel tank drain hose
• Deteriorated or contaminated fuel
Fuel pump
• Defective fuel pump
Throttle body
• Deteriorated or contaminated fuel
• Sucked-in air
8-1
TRBL
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SHTG