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:

Installing the crankshaft
1. Install: Crankshaft "1" NOTE: Install the crankshaft with the crankshaft installer pot "2", crankshaft installer bolt "3", adapter (M12) "4" and spacer (crankshaft installer) "5". CAUTION:To avoid scratching the crankshaft and to ease the installation procedure, lubricate ...

Checking the rear brake master cylinder
1. Check: Brake master cylinder Damage/scratches/wear Replace. Brake fluid delivery passages (brake master cylinder body) Obstruction Blow out with compressed air. 2. Check: Brake master cylinder kit Damage/scratches/wear Replace. 3. Check: Brake fluid reservoir Cracks/ ...

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 ...