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:

Lubricating the drive chain
The drive chain consists of many interacting parts. If the drive chain is not maintained properly, it will wear out quickly. Therefore, the drive chain should be serviced, especially when the vehicle is used in dusty areas. This vehicle has a drive chain with small rubber O-rings between eac ...

Replacing a turn signal light bulb
Remove the turn signal light lens by removing the screw. Screw Remove the burnt-out bulb by pushing it in and turning it counterclockwise. Insert a new bulb into the socket, push it in, and then turn it clockwise until it stops. Install the lens by installing ...

Checking the crankshaft
1. Measure: Crankshaft runout Out of specification Replace the crankshaft, bearing or both. NOTE: Turn the crankshaft slowly. 2. Measure: Big end side clearance Out of specification Replace the crankshaft. 3. Measure: Crankshaft width Out of specification&nbs ...