Yamaha YZF-R125 Service Manual: Checking the cylinder head

Yamaha YZF-R125 Service Manual / Engine / Cylinder head / Checking the cylinder head

1. Eliminate:

Combustion chamber carbon deposits (with a rounded scraper)

NOTE:

Do not use a sharp instrument to avoid damaging or scratching:

Spark plug bore threads
Valve seats

Checking the cylinder head

2. Check:

Cylinder head Damage/scratches Replace.

Cylinder head water jacket Mineral deposits/rust
Eliminate.

3. Measure:

Cylinder head warpage Out of specification Resurface
the cylinder head.

a. Place a straightedge "1" and a thickness gauge "2" across the cylinder head.

Checking the cylinder head

b. Measure the warpage.

c. If the limit is exceeded, resurface the cylinder head as follows.

d. Place a 400-600 grit wet sandpaper on the surface plate and resurface the cylinder head using a figure-eight sanding pattern.

NOTE:

To ensure an even surface, rotate the cylinder head several times.

Removing the cylinder head

1. Align: "I" mark "a" on the generator rotor (with the stationary pointer "b" on the generator cover) a. Turn the crankshaft counterclockwise. b. When the piston is at TDC on the compre ...

Checking the camshaft sprocket and timing chain guide

1. Check: Camshaft sprocket More than 1/4 tooth wear "a" Replace the camshaft sprocket, timing chain and crankshaft as a set. a. 1/4 tooth b. Correct 1. Timing chain roller 2. C ...

Other materials:

Circuit diagram
4. Main fuse 5. Main switch 9. Battery 14.Neutral switch 25.ECU (engine control unit) 31.Fuel sender 34.Rear brake light switch 35.Front brake light switch 37.Tail/brake light 38.Rear right turn signal light 39.Rear left turn signal light 40.Front right turn signal light 41.Front lef ...

Checking and lubricating the sidestand
Checking and lubricating the sidestand The operation of the sidestand should be checked before each ride, and the sidestand pivot and metal-to-metal contact surfaces should be lubricated if necessary. WARNING If the sidestand does not move up and down smoothly, have a Yamaha deal ...

Checking the steering
Worn or loose steering bearings may cause danger. Therefore, the operation of the steering must be checked as follows at the intervals specified in the periodic maintenance and lubrication chart. Place a stand under the engine to raise the front wheel off the ground. WARNING! To ...