Compression System; Poor Idle Speed Performance; Poor Medium-And High-Speed Performance - Yamaha XVS650 Service Manual

STARTING FAILURE/HARD STARTING/POOR IDLE SPEED
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PERFORMANCE/POOR MEDIUM-AND HIGH-SPEED PERFORMANCE,
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COMPRESSION SYSTEM
Cylinder and cylinder head
• Loose spark plug
• Loose cylinder head or cylinder
• Faulty cylinder head gasket
• Worn, damaged or seized cylinder
• Improperly sealed valve
• Improper valve-to-valve seat contact
• Improper valve timing
• Faulty valve spring
EB901000
POOR IDLE SPEED PERFORMANCE
POOR IDLE SPEED PERFORMANCE
Carburetor
• Improperly returned starter plunger
• Loose pilot jet
• Clogged pilot air jet
• Improperly synchronized carburetors
• Improperly adjusted idle speed
(th rottle stop screw)
• Improper throttle cable free play
• Flooded carburetor
Piston and piston ring
• Improperly installed piston ring
• Worn, fatigued or broken piston ring
• Seized piston ring
• Seized or damaged piston
Crankcase and crankshaft
• Improperly seated crankcase
• Seized crankshaft
Electrical system
• Faulty battery
• Faulty spark plug
• Faulty ignitor unit
• Faulty pickup coil
• Faulty ignition coil
Valve train
• Improperly adjusted valve clearance
Air filter
• Clogged air filter element
EB902000
POOR MEDIUM-AND HIGH-SPEED PERFORMANCE
POOR MEDIUM-AND HIGH-SPEED PERFORMANCE
Refer to "STARTING FAILURE/HARD STARTING". (Fuel system, electrical system, compres-
sion system and valve train)
Carburetor
• Faulty diaphragm
• Improperly adjusted fuel level
• Clogged or loose main jet
Air filter
• Clogged air filter element
Fuel pump
• Faulty fuel pump