Snowmobile Yamaha FX10X, FX10RTX, FX10RTRX, FX10RTRAX, FX10MTX, FX10MTRX, FX10MTRAX. Manual - part 54

5-36

ENG

VALVES AND VALVE SPRINGS

11. Measure:

• Valve spring free length 

a 

Out of specification 

→ Replace the valve

spring.

12. Measure:

• Compressed valve spring force 

a 

Out of specification 

→ Replace the valve

spring.

b Installed length

Valve spring free length (intake and 
exhaust):

39.57 mm (1.56 in)
<Limit>: 37.59 mm (1.48 in)

Compressed valve spring force 
(installed):

112.30 ~ 129.30 N at 34.60 mm
(11.45 ~ 13.18 kg at 34.60 mm, 
25.24 ~ 29.07 lb at 1.36 in)

13. Measure:

• Valve spring tilt 

a 

Out of specification 

→ Replace the valve

spring.

Maximum valve spring tilt:

2.5°/1.7 mm (2.5°/0.07 in)

14. Inspect:

• Valve lifter

Damage/scratches 

→ Replace the valve lift-

ers and cylinder head.

INSTALLATION

1. Deburr:

• Valve stem end

(with an oil stone)

5-37

ENG

VALVES AND VALVE SPRINGS

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 
• Valve spring 4 
• Upper spring seat 5 

(into the cylinder head)

NOTE:

• Make sure each valve is installed in its original

place. 

• Install the valve spring with the larger pitch 

a fac-

ing up. 

b Smaller pitch

New

4. Install:

• Valve cotters

NOTE:

Install the valve cotters by compressing the valve
spring with the valve spring compressor 1 and
valve spring compressor attachment 2. 

Valve spring compressor:

90890-04019, YM-04019

Valve spring compressor attach-
ment:

90890-04114

Valve spring compressor adapter 
19.5 mm:

YM-04114

5-38

ENG

VALVES AND VALVE SPRINGS

5. To secure the valve cotters onto the valve stem,

lightly tap the valve tip with a soft-face hammer.

CAUTION:

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

6. Lubricate: 

• Valve pad
• Valve lifter

(with the recommended lubricant)

7. Install:

• Valve pad
• Valve lifter

NOTE:

• The valve lifter must move smoothly when rotated

with a finger. 

• Each valve lifter and valve pad must be rein-

stalled in its original position. 

Recommended lubricant:

Molybdenum disulfide oil

5-39

ENG

AC MAGNETO ROTOR AND STARTER CLUTCH

AC MAGNETO ROTOR AND STARTER CLUTCH

i

Order

Job name/Part name

Q’ty

Remarks

AC magneto rotor and starter clutch 
removal

Remove the parts in the order listed below.

Engine assembly

Refer to “ENGINE ASSEMBLY”.

1

AC magneto rotor cover

1

2

AC magneto rotor cover gasket

1

3

Dowel pin

2

4

Stator coil

1

5

AC magneto rotor

1

6

Starter clutch

1

7

Woodruff key

1

8

Starter clutch gear

1

9

Washer

1

10

Idle gear shaft

1

11

Starter clutch idle gear

1

For installation, reverse the removal proce-
dure.

LT

E

E

E

LT

LT

LT

10

11

8

9

6

4

5

1

(11)

(3)

(3)

2

3

3

È

É

É

Ê

È

12 Nm (1.2 m 

•

 kg, 8.7 ft 

•

 lb)

10 Nm (1.0 m 

•

 kg, 7.2 ft 

•

 lb)

130 Nm (13.0 m 

•

 kg, 94 ft 

•

 lb)

È:

É:

Ê:

New

7

É

LS