Yamaha YFM45FAR, YFM450FAR. Service Manual - part 9

4 - 2

ENG

ENGINE REMOVAL

Order

Job name/Part name

Q’ty

Remarks

6

Final drive gear case breather hose

1

7

Cylinder head breather hose

1

8

Vacuum chamber breather hose

1

9

Air filter case

1

For installation, reverse the removal 
procedure.

4 - 3

ENG

ENGINE REMOVAL

SELECT LEVER UNIT AND COOLANT RESERVOIR

Order

Job name/Part name

Q’ty

Remarks

Removing the select lever unit and 
coolant reservoir

Remove the parts in the order below.

1

Shift arm

1

2

Select lever shift rod

1

3

Select lever unit

1

4

Coolant reservoir breather hose

1

5

Coolant reservoir hose

1

6

Coolant reservoir

1

For installation, reverse the removal 
procedure.

4 - 4

ENG

ENGINE REMOVAL

HOSES AND LEADS

Order

Job name/Part name

Q’ty

Remarks

Removing the hoses and leads

Remove the parts in the order below.

Water pump inlet hose

Refer to “WATER PUMP” in CHAPTER 5.

1

Cylinder head breather hose

1

2

Spark plug lead

1

3

Thermo switch 1 lead

1

4

Starter motor lead

1

5

A.C. magneto lead coupler

2

6

Speed sensor lead coupler

1

7

Reverse switch lead

1

Green/White

8

Neutral switch lead

1

Sky blue

9

High-range switch

1

Blue/White

10

Low-range switch

1

White/Red

11

Engine ground lead

1

For installation, reverse the removal 
procedure.

4 - 5

ENG

ENGINE REMOVAL

ENGINE MOUNTING BOLTS

Order

Job name/Part name

Q’ty

Remarks

Removing the engine mounting bolts

Remove the parts in the order below.

Rear wheels

Refer  to  “FRONT AND REAR WHEELS”
in CHAPTER 8.

Swingarm

Refer to “REAR SHOCK ABSORBER
AND SWINGARM” in CHAPTER 8.

1

Engine mounting bolt (rear-lower)/nut

1/1

2

Engine mounting bolt (rear-upper)/nut

1/1

3

Engine bracket bolt (front-lower)

4

4

Engine mounting bolt (font-lower)

2

5

Engine bracket (front-lower)

2

6

Engine bracket bolt (front-upper)

2

7

Engine mounting bolt (front-upper)/nut

1/1

8

Engine bracket (front-upper)

1

CAUTION:

Install all of the bolts/nuts and then
tighten them to full torque
specifications.

Refer to “INSTALLING THE ENGINE”.

4 - 6

ENG

ENGINE REMOVAL

Order

Job name/Part name

Q’ty

Remarks

9

Engine assembly

1

NOTE:

Remove the engine assembly from the
left side of the machine.

For installation, reverse the removal 
procedure.

4 - 7

ENG

INSTALLING THE ENGINE

1.Install:

●

Engine bracket (front upper) 

1

●

Engine mount bolt (front upper)/nut 

2

●

Engine bracket bolt (front upper) 

3

●

Engine bracket (front lower) 

4

●

Engine mount bolt (front lower) 

5

●

Engine bracket bolt (front lower) 

6

●

Engine mount bolt (rear upper)/nut 

7

●

Engine mount bolt (rear lower)/nut 

8

NOTE:

Do not fully tighten the bolts and nuts.

2.Tighten:

●

Engine mount bolt (front upper)/nut 

2

●

Engine bracket bolt (front upper) 

3

●

Engine mount bolt (front lower) 

5

●

Engine bracket bolt (front lower) 

6

●

Engine mount bolt (rear upper)/nut 

7

●

Engine mount bolt (rear lower)/nut 

8

T

 

R

.

.

42 Nm (4.2 m • kg, 30 ft • lb)

T

 

R

.

.

33 Nm (3.3 m • kg, 24 ft • lb)

T

 

R

.

.

42 Nm (4.2 m • kg, 30 ft • lb)

T

 

R

.

.

33 Nm (3.3 m • kg, 24 ft • lb)

T

 

R

.

.

56 Nm (5.6 m • kg, 40 ft • lb)

T

 

R

.

.

56 Nm (5.6 m • kg, 40 ft • lb)

ENGINE REMOVAL

4 - 8

ENG

CYLINDER HEAD

CYLINDER HEAD

Order

Job name/Part name

Q’ty

Remarks

Removing the cylinder head

Remove the parts in the order below.

Fuel tank/rubber cover

Refer to “SEAT, CARRIERS, FENDERS
AND FUEL TANK” in CHAPTER 3.

Front fender/air filter case
Air duct assembly 1

Refer to “ENGINE REMOVAL”.

Exhaust pipe/muffler
Carburetor assembly

Refer to “CARBURETOR” in CHAPTER 6.

Recoil starter/timing plug

Refer  to  “ADJUSTING THE VALVE
CLEARANCE” in CHAPTER 3.

Thermostat

Refer to “THERMOSTAT” in CHAPTER 5.

1

Spark plug lead

1

2

Spark plug

1

3

Engine mount bolt (upper)/nut

1/1

4

Engine bracket (upper)

1

4 - 9

ENG

CYLINDER HEAD

Order

Job name/Part name

Q’ty

Remarks

5

Cylinder head breather hose

1

6

Camshaft sprocket cover/O-ring

1/1

7

Tappet cover/O-ring

2/2

8

Thermo switch 1 lead

1

Disconnect.

9

Timing chain tensioner cap bolt

1

Refer to “REMOVING/INSTALLING THE
CYLINDER HEAD”.

10

Timing chain tensioner/gasket

1/1

11

Camshaft sprocket

1

12

Cylinder head

1

13

Cylinder head gasket

1

14

Dowel pin

2

15

O-ring

1

For installation, reverse the removal 
procedure.

4 - 10

ENG

CYLINDER HEAD

REMOVING THE CYLINDER HEAD

1.Align:

●

“T” mark
(with stationary pointer)

*****************************************************

Checking steps:

●

Turn the crankshaft counterclockwise with a
wrench.

●

Align the “T” mark 

1

 on the rotor with the

stationary pointer 

2

 on the crankcase cover.

When the “T” mark is aligned with the
stationary pointer, the piston is at the Top
Dead Center (T.D.C.).

NOTE:

●

When the piston is at the Top Dead Center
(T.D.C.) on the compression stroke, there
should be clearance between the valve stem
tips and their respective rocker arm adjusting
screws.

●

If there is no clearance, rotate the crankshaft
counterclockwise one turn.

*****************************************************

2.Loosen:

●

Camshaft sprocket bolt 

1

 

NOTE:

Use the rotor holding tool 

2

 to hold the starter

pulley.

Rotor holding tool:

P/N. YU-01235, 90890-01235

3.Loosen:

●

Timing chain tensioner cap bolt

4.Remove:

●

Timing chain tensioner

●

Camshaft sprocket

4 - 11

ENG

CYLINDER HEAD

NOTE:

●

Fasten a safety wire to the timing chain to
prevent it from falling into the crankcase.

●

When removing the camshaft sprocket, it is
not necessary to separate the timing chain.

5.Remove:

●

Cylinder head

NOTE:

●

Loosen the 6 mm bolts first.

●

Working in a crisscross pattern, loosen each
10 mm bolt 1/4 of a turn. After all the bolts
are loosened, remove them.

CHECKING THE TAPPET COVER

1.Check:

●

Tappet covers 

1

 

●

O-rings 

2

 

Cracks/damage 

→

 Replace.

CHECKING THE TIMING CHAIN 
TENSIONER

1.Check:

●

One-way cam operation (tensioner) 
Unsmooth operation 

→

 Replace.

CHECKING THE CAMSHAFT SPROCKET

1.Check:

●

Camshaft sprocket
Wear/damage 

→

 Replace the camshaft

sprocket and timing chain as a set.

a

1/4 of a tooth

b

Correct

1

Timing chain

2

Sprocket

4 - 12

ENG

CYLINDER HEAD

CHECKING THE CYLINDER HEAD

1.Eliminate:

●

Carbon deposits (from the combustion
chambers)
Use a rounded scraper.

NOTE:

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

●

Spark plug threads

●

Valve seats

2.Check:

●

Cylinder head
Scratches/damage 

→

 Replace.

●

Cylinder head water jacket
Mineral deposits/rust 

→

 Eliminate.

3.Measure:

●

Cylinder head warpage
Out of specification 

→

 Resurface.

*****************************************************

Measurement and resurfacing steps:

●

Place a straightedge and a feeler gauge
across the cylinder head.

●

Use a feeler gauge to measure the warpage.

●

If the warpage is out of specification,
resurface the cylinder head.

●

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

NOTE:

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

*****************************************************

Cylinder head warpage:

Less than 0.03 mm (0.0012 in)

4 - 13

ENG

CYLINDER HEAD

INSTALLING THE CYLINDER HEAD

1.Install:

●

Cylinder head

●

Bolt (M10)

●

Bolt (M6)

NOTE:

●

Lubricate the washer with engine oil.

●

Tighten the bolts (M10) in two stages and a
crisscross pattern.

T

 

R

.

.

40 Nm (4.0 m • kg, 29 ft • lb)

T

 

R

.

.

10 Nm (1.0 m • kg, 7.2 ft • lb)

2.Install:

●

Camshaft sprocket

*****************************************************

Installing steps:

●

Rotate the camshaft to align the camshaft
pin 

1

 with the cylinder head match mark 

2

.

●

Turn the crankshaft counterclockwise with a
wrench.

●

Align the “T” mark 

3

 on the rotor with the

stationary pointer 

4

 on the crankcase cover.

When the “T” mark is aligned with the
stationary pointer, the piston is at the Top
Dead Center (T.D.C.).

CAUTION:

Do not turn the crankshaft during the
camshaft sprocket installation.

●

Place the timing chain onto the camshaft
sprocket.

●

Install the camshaft sprocket onto the
camshaft and finger tighten the sprocket bolt.

4 - 14

ENG

CYLINDER HEAD

NOTE:

Be sure the “I” mark 

5

 on the camshaft

sprocket is aligned with the match mark 

2

 on

the cylinder head.

●

Force the camshaft clockwise and
counterclockwise to remove timing chain slack.

●

Insert a screwdriver into the timing chain
tensioner hole and push the timing chain
guide inward.

●

While pushing the timing chain guide, be
sure that the camshaft sprocket “I” mark 

5

 is

aligned with the cylinder head match mark

2

.

●

If the marks are aligned, tighten the camshaft
sprocket bolt. If the marks are not aligned,
change the meshing position of the camshaft
sprocket and timing chain.

*****************************************************

3.Install:

●

Timing chain tensioner

*****************************************************

Installation steps:

●

Remove the tensioner cap bolt 

1

, washer 

2

and spring 

3

.

●

Release the timing chain tensioner one-way
cam 

4

 and push the tensioner rod 

5

 all the

way in.

●

Install the tensioner 

6

 with a new gasket into

the cylinder.

WARNING

Always use a new gasket.

●

Install the spring, washer and cap bolt.

*****************************************************

T

 

R

.

.

Bolts (timing chain tensioner):

11 Nm (1.1 m • kg, 8.0 ft • lb)

T

 

R

.

.

Cap bolt (timing chain tensioner):

23 Nm (2.3 m • kg, 17 ft • lb)

4 - 15

ENG

CYLINDER HEAD

4.Tighten:

●

Camshaft sprocket bolt 

1

 

NOTE:

Use the rotor holding tool 

2

 to hold the starter

pulley.

5.Check:

●

Camshaft sprocket “I” mark

●

Rotor “T” mark
Out of alignment 

→

 Adjust.

Rotor holding tool:

P/N. YU-01235, 90890-01235

T

 

R

.

.

60 Nm (6.0 m • kg, 43 ft • lb)

4 - 16

ENG

CAMSHAFT, ROCKER ARMS AND VALVES

CAMSHAFT, ROCKER ARMS AND VALVES 

Order

Job name/Part name

Q’ty

Remarks

Removing the camshaft, rocker 
arms and valves

Remove the parts in the order below.

1

Intake manifold/O-ring

1/1

2

Thermo  switch

1

3

Oil check bolt

1

4

Lock washer/bearing retainer

1/1

5

Camshaft

1

Refer to “REMOVING/INSTALLING THE
CAMSHAFT AND ROCKER ARM”.

6

Rocker arm shaft/O-ring

2/2

7

Rocker  arm

2

8

Locknut/valve adjuster

2/2

9

Valve cotter

4

Refer to “REMOVING/INSTALLING THE 
VALVE AND VALVE SPRING”.

10

Valve spring retainer

2

11

Valve spring (outer)

2

4 - 17

ENG

CAMSHAFT, ROCKER ARMS AND VALVES

Order

Job name/Part name

Q’ty

Remarks

12

Valve spring (inner)

2

Refer to “REMOVING/INSTALLING THE
VALVE AND VALVE SPRING”.

13

Valve (intake)

1

14

Valve (exhaust)

1

15

Valve stem seal

2

16

Valve spring seat

2

For installation, reverse the removal 
procedure.