Yamaha YZF-R125 Service Manual: Poor medium-and-high-speed performance

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 throttle body joint and air filter case joint
1. Remove: Right lower side cowling Left lower side cowling Refer to "GENERAL CHASSIS" on page 4-1. 2. Check: Throttle body joint "1" Air filter case joint "2" Cracks/damage Replace. 3. Install: Right lower side cowling Left lower side cowling Refer to "GENERAL CHAS ...

Removing the valves
The following procedure applies to all of the valves and related components. NOTE: Before removing the internal parts of the cylinder head (e.g., valves, valve springs, valve seats), make sure the valves properly seal. 1. Check: Valve sealing Leakage at the valve seat Check the valve ...

Identification numbers
Record the key identification number, vehicle identification number and model label information in the spaces provided below for assistance when ordering spare parts from a Yamaha dealer or for reference in case the vehicle is stolen. KEY IDENTIFICATION NUMBER: VEHICLE IDENTIFICATION ...