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:
Assembling the front fork legs
The following procedure applies to both of the
front fork legs.
WARNING
Make sure the oil levels in both front fork
legs are equal.
Uneven oil levels can result in poor handling
and a loss of stability.
NOTE:
When assembling the front fork leg, be sure to
rep ...
Installing the steering head
1. Lubricate:
Upper bearing
Lower bearing
Bearing races
2. Install:
Lower ring nut
Rubber washer
Upper ring nut
Lock washer
Refer to "CHECKING AND ADJUSTING
THE STEERING HEAD" on page 3-22.
3. Install:
Upper bracket
Steering stem nut
NOTE:
Temporarily tighten t ...
Troubleshooting
The ignition system fails to operate (no spark or intermittent spark).
NOTE:
Before troubleshooting, remove the following part(s):
1. Seats
2. Fuel tank
3. Right side cover
4. Left side panel
5. Left upper side cowling
...