Yamaha YZF-R125 Service Manual: Poor medium-and-high-speed performance
Refer to "STARTING FAILURES" on page 9-1.
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".
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 loo ...
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 ...
Other materials:
Checking the drive sprocket
1. Check:
Drive sprocket
More than 1/4 tooth "a" wear
Replace the
drive chain sprockets as a set.
Bent teeth Replace the drive
chain sprockets
as a set.
b. Correct
1. Drive chain roller
2. Drive chain sprocket
Checking the rear wheel sprocket
Refer to "CHECKING AND R ...
Checking the crankshaft
1. Measure:
Crankshaft runout
Out of specification Replace
the crankshaft,
bearing or both.
NOTE:
Turn the crankshaft slowly.
2. Measure:
Big end side clearance
Out of specification Replace
the crankshaft.
3. Measure:
Crankshaft width
Out of specification&nbs ...
Checking the spark plug cap
1. Check:
Spark plug cap resistance
Out of specification Replace.
a. Remove the spark plug cap from the spark
plug lead.
b. Connect the pocket tester ( × 1k)
to the
spark plug cap as shown.
c. Measure the spark plug cap resistance. ...