Yamaha XMAX YP125R - Service manual > Cylinder head (YP250R)

Removing the cylinder head

Removing the cylinder head

Removing the cylinder head
Removing the cylinder head

Removing the cylinder head

1. Align:

a. Turn the primary sheave nut on the left side of the crankshaft counterclockwise to turn the crankshaft.

Removing the cylinder head

b. When the piston is at TDC on the compression stroke, align the "I" mark "c" on the camshaft sprocket with the stationary pointer "d" on the cylinder head.

Removing the cylinder head

2. Loosen:

TIP

While holding the primary sheave nut with a wrench, remove the camshaft sprocket bolt.

Removing the cylinder head

3. Remove:

TIP

To prevent the timing chain from falling into the crankcase, fasten it with a wire "3".

Removing the cylinder head

4. Remove:

TIP

Removing the cylinder head

Checking the cylinder head

1. Eliminate:

TIP

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

Checking the cylinder head

2. Check:

Damage/scratches → Replace.

Mineral deposits/rust → Eliminate.

3. Measure:

Out of specification → Resurface the cylinder head.

Warpage limit 0.05 mm (0.0020 in)

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

TIP

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

Checking the camshaft sprocket

1. Check:

More than 1/4 tooth wear "a" → Replace the camshaft sprocket, timing chain and crankshaft as a set.

Checking the camshaft sprocket

a. 1/4 tooth

b. Correct

1. Timing chain roller

2. Camshaft sprocket

Checking the timing chain tensioner

1. Check:

Cracks/damage → Replace.

2. Check:

Rough movement → Replace the timing chain tensioner housing.

Checking the camshaft sprocket

3. Check:

Damage/wear → Replace the defective part(s).

Installing the cylinder head

1. Tighten:

Cylinder head nut 22 Nm (2.2 m*kgf, 16 ft*lbf)

Cylinder head bolt 10 Nm (1.0 m*kgf, 7.2 ft*lbf)

TIP

Installing the cylinder head

2. Install:

a. Turn the primary sheave nut on the left side of the crankshaft counterclockwise to turn the crankshaft.

b. Align the "I" mark "a" on the generator rotor with the stationary pointer "b" on the generator cover.

c. Align the "I" mark "c" on the camshaft sprocket with the stationary pointer "d" on the cylinder head.

Installing the cylinder head

d. Install the timing chain onto the camshaft sprocket, and then install the camshaft sprocket onto the camshaft.

TIP

NOTICE

Do not turn the crankshaft when installing the camshaft to avoid damage or improper valve timing.

e. Install the camshaft sprocket plate and camshaft sprocket bolt.

f. While holding the primary sheave nut, temporarily tighten the camshaft sprocket bolt.

g. Remove the wire from the timing chain.

3. Install:

a. Remove the timing chain tensioner cap bolt "1" and spring "2".

b. Release the timing chain tensioner one-way cam "3" and push the timing chain tensioner rod "4" all the way into the timing chain tensioner housing.

c. Install the timing chain tensioner and gasket "5" onto the cylinder.

Timing chain tensioner bolt 10 Nm (1.0 m*kgf, 7.2 ft*lbf)

d. Install the spring and timing chain tensioner cap bolt.

Timing chain tensioner cap bolt 8 Nm (0.8 m*kgf, 5.8 ft*lbf)

Checking the camshaft sprocket

4. Turn:

5. Check:

Make sure the "I" mark "a" on the generator rotor is aligned with the stationary pointer "b" on the generator cover.

Make sure the "I" mark "c" on the camshaft sprocket is aligned with the stationary pointer "d" on the cylinder head.

Out of alignment → Correct.

Refer to the installation steps above.

Installing the cylinder head

6. Tighten:

Camshaft sprocket bolt 60 Nm (6.0 m*kgf, 43 ft*lbf)

NOTICE

Be sure to tighten the camshaft sprocket bolt to the specified torque to avoid the possibility of the bolt coming loose and damaging the engine.

7. Measure:

Out of specification → Adjust.

See also:

 Yamaha XMAX YP125R - Service manual > Engine removal (YP250R)

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 Yamaha XMAX YP125R - Service manual > Camshaft (YP250R)

Removing the rocker arms and camshaft Removing the rocker arms and camshaft

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