Yamaha XMAX YP125R - Service manual > Checking the valve springs

The following procedure applies to all of the valve springs.

1. Measure:

• Valve spring free length "a"

Out of specification → Replace the valve spring.

Inner spring Free length (intake) 38.10 mm (1.50 in)

Limit 36.10 mm (1.42 in)

Free length (exhaust) 38.10 mm (1.50 in)

Limit 36.10 mm (1.42 in)

Outer spring

Free length (intake) 36.93 mm (1.45 in)

Limit 35.00 mm (1.38 in)

Free length (exhaust) 36.93 mm (1.45 in)

Limit 35.00 mm (1.38 in)

2. Measure:

• Compressed valve spring force "a"

Out of specification → Replace the valve spring.

Inner spring

Installed compression spring force (intake) 76-88 N (7.75-8.97 kgf, 17.08- 19.78 lbf)

Installed compression spring force (exhaust) 76-88 N (7.75-8.97 kgf, 17.08- 19.78 lbf)

Installed length (intake) 30.10 mm (1.19 in)

Installed length (exhaust) 30.10 mm (1.19 in)

Outer spring

Installed compression spring force (intake) 115-133 N (11.73-13.56 kgf, 25.85-29.90 lbf)

Installed compression spring force (exhaust) 115-133 N (11.73-13.56 kgf, 25.85-29.90 lbf)

Installed length (intake) 31.60 mm (1.24 in)

Installed length (exhaust) 31.60 mm (1.24 in)

b. Installed length

3. Measure:

• Valve spring tilt "a"

Out of specification → Replace the valve spring.

Inner spring

Spring tilt (intake) 2.5º/1.7 mm

Spring tilt (exhaust) 2.5º/1.7 mm

Outer spring

Spring tilt (intake) 2.5º/1.6 mm

Spring tilt (exhaust) 2.5º/1.6 mm

Installing the valves

The following procedure applies to all of the valves and related components.

1. Deburr:

• Valve stem end (with an oil stone)

2. Lubricate:

• Valve stem "1"
• Valve stem seal "2" (with the recommended lubricant)

Recommended lubricant Molybdenum disulfide oil

3. Install:

• Lower spring seat "1"
• Valve stem seal "2"
• Valve "3"
• Inner valve spring "4"
• Outer valve spring "5"
• Upper spring seat "6" (into the cylinder head)

TIP

Make sure each valve is installed in its original place.

Install the valve springs with the larger pitch "a" facing up.

b. Smaller pitch

4. Install:

• Valve cotters "1"

TIP

Install the valve cotters by compressing the valve spring with the valve spring compressor and the valve spring compressor attachment "2".

Valve spring compressor 90890-04019

YM-04019

Valve spring compressor attachment

90890-04108

Valve spring compressor adapter 22 mm

YM-04108

5. To secure the valve cotters onto the valve stem, lightly tap the valve tip with a soft-face hammer.

NOTICE

Hitting the valve tip with excessive force could damage the valve.

See also: