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:

Separating the crankcase
1. Remove: Crankcase bolts NOTE: Loosen each bolt 1/4 of a turn at a time, in stages and in the proper sequence as shown. A. Right crankcase B. Left crankcase 2. Turn: Shift drum segment NOTE: Turn the shift drum segment "1" to the position shown in the illustration. In this ...

Cast wheels
To maximize the performance, durability, and safe operation of your vehicle, note the following points regarding the specified wheels. The wheel rims should be checked for cracks, bends or warpage before each ride. If any damage is found, have a Yamaha dealer replace the wheel. ...

Checking the timing chain tensioner
1. Check: Timing chain tensioner Cracks/damage/rough movement Replace. a. Lightly press the timing chain tensioner rod into the timing chain tensioner housing by hand. NOTE: While pressing the timing chain tensioner rod, wind it clockwise with a thin screwdriver "1" until it stops. b. ...