Yamaha YFM660 01 User Manual

6 - 12
COOLWATER PUMP
2.Check:

Water pump seal

Oil seal 

Water pump outlet pipe
Cracks/damage/wear →
 Replace.

Bearing
Rough movement →
 Replace. 
New
ASSEMBLING THE WATER PUMP
1.Install:

Oil seal 1
 
(into the water pump housing 2
)
OTE:

Before installing the oil seal, apply tap water
or coolant onto its outer surface.

Install the oil seal with a socket 3
 that
matches its outside diameter.
2.Install:

Water pump seal 1
 
(into the water pump housing 2
)
CAUTION:
Never lubricate the water pump...

6 - 13
COOLWATER PUMP
4.Measure:

Impeller shaft tilt
Out of specification →
 Repeat steps (3) and
(4).
CAUTION:
Make sure that the rubber damper and rub-
ber damper holder are bottom with the
impeller.
1Straightedge
2Impeller
Max. impeller shaft tilt:
0.15 mm (0.006 in) 

7 - 1
CARBCARBURETORS
CARBURETION
CARBURETORS
Order Job name/Part name Q’ty Remarks
Removing the carburetors
Remove the parts in the order below.
Seat/front fender/fuel tank/rubber cover 
2Refer to “SEAT, FENDERS AND FUEL 
TANK” in CHAPTER 3.
1 Air vent hose 2
2 Float chamber breather hose 1
3 Starter cable/starter plunger 1/1
4 Throttle valve cover 1
5 Throttle cable end 1
6 Throttle cable 1
7 Clamp screw (air filter case) 2 Loosen.
8 Clamp screw (carburetor joint) 2 Loosen.
9 Carburetors 1
For...

7 - 2
CARBCARBURETORS
Order Job name/Part name Q’ty Remarks
Separating the carburetors
Remove the parts in the order below.
1 Drain hose 2
2 Plate 1
3 Connecting bolt/spacer 2/2
4Spring 1
5Hose joint 1
6Pipe 1
7 Carburetor 2 1
8 Carburetor 1 1
For installation, reverse the separating
procedure. 

7 - 3
CARBCARBURETORS
Order Job name/Part name Q’ty Remarks
Disassembling the carburetor
Remove the parts in the order below.
1
  Throttle stop screw 1
2
  Vacuum chamber cover 1
3
 Spring 1
4
  Jet needle holder 1
5
 Spring 1
6
  Jet needle set 1
7
 Piston valve 1
8
 Float chamber 1
9
 Drain screw  1
0
  Float 1 Refer to “ASSEMBLING THE CARBURE-
TOR”.
A
 Needle valve set 1 

7 - 4
CARBCARBURETORS
Order Job name/Part name Q’ty Remarks
B
 Pilot jet 1
C
  Pilot screw set 1 Refer to “DISASSEMBLING/
ASSEMBLING THE CARBURETOR”.
OTE:
Before disassembling the carburetor,
make sure to note the number of times
the pilot screw is turned out from the
seated position to its set position.
D
 Main jet 1
E
  Needle jet 1 Refer to “ASSEMBLING THE CARBURE-
TOR”.
F
 Starter jet 1
G
 Pilot air jet 1
For assembly, reverse the disassembly
procedure. 

7 - 5
CARBCARBURETORS
DISASSEMBLING THE CARBURETOR
OTE:
Before disassembling the carburetor, make
sure to note the number of times the pilot
screw is turned out from the seated position to
its set position.
CHECKING THE CARBURETOR
1.Check:

Carburetor body

Float chamber
Cracks/damage →
 Replace.

Fuel passage
Contamination →
 Clean as indicated.

Fuel chamber body 
Contamination →
 Clean.
***********************************************
Cleaning steps:

Wash the carburetor in a petroleum based
solvent....

7 - 6
CARBCARBURETORS
4.Check:

Piston valve 1
 
Scratches/wear/damage →
 Replace.

Rubber diaphragm 2
 
Tears →
 Replace.
5.Check:

Vacuum chamber cover 1
 

Spring 2
 
Cracks/damage →
 Replace.
6.Check:

Jet needle 1
 

Main jet 2
 

Needle jet 3
 

Pilot air jet 4
 

Pilot jet 5
 

Pilot screw 6
 

Starter jet 7
 

Starter plunger 8
 
Bends/wear/damage →
 Replace.

Blockage →
 Blow out the jets with
compressed air.
7.Check:

Free movement (piston valve)
Sticks →
 Replace the piston valve guide and
the...

7 - 7
CARBCARBURETORS
ASSEMBLING THE CARBURETOR
CAUTION:
Before reassembling, wash all of the parts
in a clean petroleum based solvent.
1.Install:

Pilot screw 1
 
OTE:
Before assembling the carburetor, make sure
to turn out the pilot screw the same number of
times, as noted before disassembly, from the
seated position to the set position.
2.Measure:

Float height a
 
Out of specification →
 Adjust.
***********************************************
Measurement and adjustment steps:

Hold the carburetor in...

7 - 8
CARBCARBURETORS
3.Install:

Carburetor 1

Carburetor 2

Pipe

Hose joint

Spring
OTE:

Install the throttle valve lever 1
 onto
carburetor 2 between the spring 2
 and
synchronizing screw 3
.

Make sure the throttle valves operate
smoothly and that the synchronization is
correct.
ADJUSTING THE FUEL LEVEL
1.Measure:

Fuel level a
 
Out of specification →
 Adjust. 
Fuel level:
3 ~ 4 mm (0.12 ~ 0.16 in)
Below the float chamber mating
surface
***********************************************
Fuel level...