Yamaha YFM660 01 User Manual

							3 - 5
CHK
ADJ
SEAT, FENDERS AND FUEL TANK
REAR FENDER
Order Job name/Part name Q’ty Remarks
Removing the rear fender
Remove the parts in the order below.
Seat Refer to “SEAT, FRONT PANEL, FOOT-
REST GUARDS AND ENGINE SKID 
PLATE”.
Front fender Refer to “HEADLIGHTS AND FRONT 
FENDER”.
1 Battery holding bracket 1
2 Battery lead 2 Disconnect.
CAUTION:
First disconnect the negative lead,
then disconnect the positive lead.
3 Battery 1
4 Rear fender 1
For installation, reverse the removal pro-
cedure. 
						

							3 - 6
CHK
ADJ
SEAT, FENDERS AND FUEL TANK
FUEL TANK
Order Job name/Part name Q’ty Remarks
Removing the fuel tank
Remove the parts in the order below.
Seat and front panel Refer to “SEAT, FRONT PANEL, FOOT-
REST GUARDS AND ENGINE SKID 
PLATE”.
Front fender Refer to “HEADLIGHTS AND FRONT 
FENDER”.
1 Fuel hose 1
NOTE:
Before disconnecting the fuel hose, turn
the fuel cock to “OFF”.
2 Fuel tank 1
NOTE:
When installing the fuel tank, pass the
fuel tank breather hose through the hole
in the handlebar protector.
3 Plastic band 2 
						

							3 - 7
CHK
ADJ
SEAT, FENDERS AND FUEL TANK
Order Job name/Part name Q’ty Remarks
4 Rubber cover 1 1
5 Rubber cover 2 1
6 Hose holder 2
For installation, reverse the removal pro-
cedure. 
						

							3 - 8
CHK
ADJ
ADJUSTING THE VALVE CLEARANCE
ENGINE
ADJUSTING THE VALVE CLEARANCE
NOTE:

The valve clearance must be adjusted when
the engine is cool to the touch.

Adjust the valve clearance when the piston is
at the Top Dead Center (T.D.C.) on the com-
pression stroke.
1.Remove:

Seat 

Front fender 

Fuel tank
Refer to “SEAT, FENDERS AND FUEL
TANK”.
2.Remove:

Tappet cover (intake) 1
 

Tappet covers (exhaust) 2
 
3.Disconnect:

Spark plug cap 3
 
4.Remove:

Spark plug
5.Remove:

Crankshaft end accessing screw 1
 

Timing mark accessing screw 2
  
						

							3 - 9
CHK
ADJ
ADJUSTING THE VALVE CLEARANCE
6.Check:

Valve clearance
Out of specification →
 Adjust.
***********************************************
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, 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.
Valve clearance (cold):
Intake:
0.10 ~ 0.15 mm
(0.0039 ~ 0.0059 in)
Exhaust:
0.15 ~ 0.20 mm
(0.0059 ~ 0.0079 in)

Measure the valve clearance using a feeler
gauge 3
.
*********************************************** 
						

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CHK
ADJ
ADJUSTING THE VALVE CLEARANCE
7.Adjust:

Valve clearance 
***********************************************
Adjustment steps:

Loosen the locknut 1
.

Insert a feeler gauge 2
 between the adjuster
end and the valve end.

Turn the adjuster 3
 clockwise or counter-
clockwise with the tappet adjusting tool 4
until the proper clearance is obtained.

Hold the adjuster to prevent it from moving
and then tighten the locknut.

Measure the valve clearance.

If the clearance is incorrect, repeat the above
steps until the proper clearance is obtained.
***********************************************
Tappet adjusting tool:
P/N. YM-08035, 90890-01311
T R..
Locknut:
14 Nm (1.4 m  kg, 10 ft  lb)
8.Install:

All removed parts
NOTE:
Install all removed parts in the reverse order of
their disassembly. Note the following points.
9.Install:

Spark plug 

Tappet cover (intake)

Tappet covers (exhaust)
T R..18 Nm (1.8 m  kg, 13 ft  lb)
T R..10 Nm (1.0 m  kg, 7.2 ft  lb)
T R..12 Nm (1.2 m  kg, 8.7 ft  lb) 
						

							3 - 11
CHK
ADJADJUSTING THE VALVE CLEARANCE/ADJUSTING THE
TIMING CHAIN/ADJUSTING THE IDLING SPEED
10.Install:

Fuel tank

Front fender 

Seat
Refer to “SEAT, FENDERS AND FUEL
TANK”.
ADJUSTING THE TIMING CHAIN
Adjustment free.
ADJUSTING THE IDLING SPEED
1.Start the engine and let it warm up for sev-
eral minutes.
2.Attach:

Tachometer 
(to the spark plug lead)
3.Check:

Engine idling speed
Out of specification →
 Adjust.
Engine idling speed:
1,450 ~ 1,550 r/min 
						

							3 - 12
CHK
ADJADJUSTING THE IDLING SPEED/
ADJUSTING THE THROTTLE LEVER FREE PLAY
4.Adjust:

Engine idling speed
***********************************************
Adjustment steps:

Turn the throttle stop screw 1
 in or out until
the specified idling speed is obtained.
***********************************************
5.Detach:

Tachometer
6.Adjust:

Throttle lever free play
Refer to “ADJUSTING THE THROTTLE
LEVER FREE PLAY”. Turning inIdling speed becomes 
higher.
Turning outIdling speed becomes 
lower.
ADJUSTING THE THROTTLE LEVER FREE 
PLAY
NOTE:
Engine idling speed should be adjusted prop-
erly before adjusting the throttle lever free
play.
1.Check:

Throttle lever free play a
 
Out of specification →
 Adjust. 
Throttle lever free play:
3 ~ 5 mm (0.12 ~ 0.20 in) 
						

							3 - 13
CHK
ADJ
ADJUSTING THE THROTTLE LEVER FREE PLAY
2.Adjust:

Throttle lever free play
***********************************************
Adjustment steps:
First step:

Pull back the adjuster cover 1
.

Loosen the locknut 2
 on the carburetor side. 

Turn the adjuster 3
 in or out until the correct
free play is obtained.

Tighten the locknut 2
.

Push in the adjuster cover 1
.
NOTE:
If the free play cannot be adjusted here, adjust
it at the throttle lever side of the cable.
Second step:

Pull back the adjuster cover 4
.

Loosen the locknut 5
.

Turn the adjuster 6
 in or out until the correct
free play is obtained.

Tighten the locknut 5
.

Push in the adjuster cover 4
.
WARNING
After adjusting the free play, turn the handle-
bar to the right and left to make sure that the
engine idling speed does not increase.
***********************************************
Turning in Free play is increased.
Turning out Free play is decreased.
Turning in Free play is increased.
Turning out Free play is decreased. 
						

							3 - 14
CHK
ADJ
ADJUSTING THE SPEED LIMITER
ADJUSTING THE SPEED LIMITER
The speed limiter keeps the carburetor throttle
from becoming fully-opened even when the
throttle lever is applied to the maximum posi-
tion. Screwing in the adjuster stops the engine
speed from increasing.
1.Check:

Speed limiter length a
 
Out of specification →
 Adjust.
Speed limiter length:
12 mm (0.47 in)
2.Adjust:

Speed limiter length
***********************************************
Speed limiter length adjustment steps:

Loosen the locknut 1
.

Turn the adjuster 2
 in or out until the speci-
fied speed limiter length is obtained.

Tighten the locknut.
WARNING

Particularly for a beginner rider, the
speed limiter should be screwed in com-
pletely. Screw it out little by little as their
riding technique improves. Never remove
the speed limiter for a beginning rider.

For proper throttle lever operation do not
turn out the adjuster more than 12 mm
(0.47 in). Also, always adjust the throttle
lever free play to 3 ~ 5 mm (0.12 ~ 0.20 in).
***********************************************
Turning inSpeed limiter length is 
decreased.
Turning outSpeed limiter length is 
increased.