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:

Setting the diagnostic mode
1. Set the main switch to "OFF" and the engine stop switch to " ". 2. Disconnect the self-diagnosis signal connector "1", and then connect the FI diagnostic tool "2" as shown. 3. Disconnect the fuel pump coupler. 4. While pressing the "MODE" button, set the main switch to "ON". NOTE: ...

Parking
When parking, stop the engine, and then remove the key from the main switch. WARNING Since the engine and exhaust system can become very hot, park in a place where pedestrians or children are not likely to touch them and be burned. Do not park on a slope or on soft ground, ...

Replacing the air filter element and cleaning the check hose
The air filter element should be replaced at the intervals specified in the periodic maintenance and lubrication chart. Have a Yamaha dealer replace the air filter element more frequently if you are riding in unusually wet or dusty areas. In addition, the air filter check hose must be ...