Yamaha YFM660 01 User Manual

5 - 1
ENGENGINE REMOVAL
ENGINE
ENGINE REMOVAL
MUFFLER AND EXHAUST PIPES
Order Job name/Part name Q’ty Remarks
Removing the muffler and exhaust 
pipesRemove the parts in the order below.
Seat/left footrest guard/engine
Refer to “SEAT, FENDERS AND FUEL 
TANK” in CHAPTER 3. Skid plate
Front and rear fenders
Fuel tank and rubber covers
1 Muffler 1
2 Exhaust pipe 1 1
3 Exhaust pipe 2 1
For installation, reverse the removal pro-
cedure. 

5 - 2
ENGENGINE REMOVAL
LEFT FOOTREST
Order Job name/Part name Q’ty Remarks
Removing the left footrest
Remove the parts in the order below.
1 Locknut 1
2 Locknut 1 Left-hand threads
3 Adjusting rod 1
4 Left footrest guard bracket 1
5 Left footrest 1
For installation, reverse the removal pro-
cedure. 

5 - 3
ENGENGINE REMOVAL
LEADS, CABLES AND HOSES
Order Job name/Part name Q’ty Remarks
Removing the leads, cables and 
hosesRemove the parts in the order below.
Engine oil Drain.
Coolant Drain.
Water jacket outlet pipe Refer to “THERMOSTAT” in CHAPTER 6.
Radiator outlet hose Refer to “WATER PUMP” in CHAPTER 6.
Carburetors Refer to “CARBURETORS” in CHAPTER 
7.
Rear shock absorber and connecting 
armRefer to “REAR SHOCK ABSORBER 
AND RELAY ARM” in CHAPTER 4.
Drive sprocket and swingarm Refer to “SWINGARM...

5 - 4
ENGENGINE REMOVAL
Order Job name/Part name Q’ty Remarks
4 Coupler 5 Disconnect.
5 Speed sensor/O-ring 1/1
6 Neutral switch lead/reverse switch lead 1/1
7 Ground lead 1
8 Clutch cable 1
9 Parking brake cable 1
10 Reverse control cable 1
11 Oil pipe 2 1 Disconnect.
12 Oil pipe 1 1 Disconnect.
13 Oil tank breather hose 1 Disconnect.
14 Crankcase breather hose 1 Disconnect.
For installation, reverse the removal pro-
cedure. 

5 - 5
ENGENGINE REMOVAL
ENGINE MOUNTING BOLTS
Order Job name/Part name Q’ty Remarks
Removing the engine mounting bolt
Remove the parts in the order below.
1 Engine mounting bolt (upper)/nut 1/1
2 Engine bracket bolt (upper) 4
CAUTION:
Install all of the bolts/nuts and then
tighten them to full torque specifica-
tions.
Refer to “INSTALLING THE ENGINE”. 3 Engine bracket (upper) 1
4 Engine mounting bolt (middle)/nut 1/1
5 Engine mounting bolt (lower)/nut 1/1
6 Engine bracket (middle-left) 1
7 Engine bracket...

5 - 6
ENGENGINE REMOVAL
Order Job name/Part name Q’ty Remarks
11 Engine assembly 1
NOTE:
Remove the engine assembly from the
left side of the machine.
For installation, reverse the removal pro-
cedure. 

5 - 7
ENG
INSTALLING THE ENGINE
1.Install:

Engine brackets (lower) 1
 

Engine bracket bolts (lower) 2
 

Engine brackets (middle) 3
 

Engine mounting bolt (lower)/nut 4
 

Engine mounting bolt (middle)/nut 5
 

Engine bracket (upper) 6
 

Engine bracket bolts (upper) 7
 

Engine mounting bolt (upper)/nut 8
 
NOTE:
Do not fully tighten the bolts and nuts.
2.Install:

Swingarm

Pivot shaft/nut 9
 
NOTE:
Do not fully tighten the pivot shaft nut.
3.Tighten:

Engine bracket bolt (lower) 2
 

Engine bracket...

5 - 8
ENGCYLINDER HEAD COVER
CYLINDER HEAD COVER
Order Job name/Part name Q’ty Remarks
Removing the cylinder head cover
Remove the parts in the order below.
Seat/front fender
Refer to “SEAT, FENDERS AND FUEL 
TANK” in CHAPTER 3.
Fuel tank/rubber cover 2
1 Engine mounting bolt/nut 1/1
2 Engine bracket (front-upper) 1
3 Oil tank breather hose 1
4 Union bolt 2
5 Copper washer 4
6 Oil delivery pipe 1 1
7 Spark plug 1
8 Tappet cover (intake) 1
9 Tappet cover (exhaust) 2 

5 - 9
ENGCYLINDER HEAD COVER
Order Job name/Part name Q’ty Remarks
10 Cylinder head cover 1 Refer to “REMOVING/INSTALLING CYL-
INDER HEAD COVER”.
11 Dowel pin 2
For installation, reverse the removal pro-
cedure. 

5 - 10
ENGCYLINDER HEAD COVER
REMOVING THE CYLINDER HEAD COVER
1.Align:

“I” mark
(with stationary pointer)
***********************************************
Checking steps:

Turn the crankshaft counterclockwise with a
wrench.

Align the “I” mark 1
 on the rotor with the sta-
tionary pointer 2
 on the crankcase cover.
When the “I” mark is aligned with the station-
ary 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,...