Poor Medium-And-High-Speed Performance; Engine; Fuel System; Faulty Gear Shifting - Yamaha YBR125ED 2005 Service Manual

POOR MEDIUM-AND-HIGH-SPEED PERFORMANCE/

FAULTY GEAR SHIFTING/FAULTY CLUTCH
EAS00849
POOR MEDIUM-AND-HIGH-SPEED PERFORMANCE
Refer to "STARTING FAILURES".

ENGINE

Air filter
• Clogged air filter element
Air intake system
• Bent, clogged or disconnected carburetor
air vent hose
EAS00850

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
EAS00851

FAULTY CLUTCH

CLUTCH SLIPS

Clutch
• Improperly assembled clutch
• Improperly adjusted clutch cable
• Loose or fatigued clutch spring
• Worn friction plate
• Worn clutch plate
Engine oil
• Incorrect oil level
• Incorrect oil viscosity (low)
• Deteriorated oil

FUEL SYSTEM

Carburetor
• Faulty diaphragm
• Incorrect fuel level
• Loose or clogged main jet

JUMPS OUT OF GEAR

Shift shaft
• Incorrect shift pedal position
• Improperly returned stopper lever
Shift forks
• Worn shift fork
Shift drum
• Incorrect thrust play
• Worn shift drum groove
Transmission
• Worn gear dog

CLUTCH DRAGS

Clutch
• Unevenly tensioned clutch springs
• Warped pressure plate
• Bent clutch plate
• Swollen friction plate
• Bent clutch push rod
• Broken clutch boss
• Burnt primary driven gear bushing
• Match marks not aligned
Engine oil
• Incorrect oil level
• Incorrect oil viscosity (high)
• Deteriorated oil
8 - 3
TRBL
SHTG