Yamaha YFM660 01 User Manual

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ENGCRANKSHAFT AND BALANCER
INSTALLING THE CRANKSHAFT
1.Install:

Crankshaft
NOTE:
Hold the connecting rod at the Top Dead Cen-
ter (TDC) with one hand while turning the nut
of the installing tool with the other. Operate the
installing tool until the crankshaft bottoms
against the bearing.
CAUTION:
Apply engine oil to each bearing to protect
the crankshaft against scratches and to
make installation easier.
Crankshaft installer pot 1:
P/N. 90890-01274
Crankshaft installer bolt 2:
P/N. 90890-01275...

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ENGTRANSMISSION
TRANSMISSION
Order Job name/Part name Q’ty Remarks
Removing the transmission
Remove the parts in the order below.
Crankcase Separate. Refer to “CRANKCASE”.
1 Shift fork guide bar (short) 1
Refer to “INSTALLING THE TRANSMIS-
SION”. 2 Shift fork “C” 1
3 Shift fork guide bar (long) 1
4 Shift fork “R” 1
5 Shift fork “L” 1
6 Shift drum 1
7 Reverse shift shaft 1
8 Main axle assembly 1
9 Spacer/O-ring 1/1
10 Drive axle 1 

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ENGTRANSMISSION
Order Job name/Part name Q’ty Remarks
11 Counter axle 1
12 Counter gear 1
For installation, reverse the removal pro-
cedure. 

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ENGTRANSMISSION
MAIN AXLE
Order Job name/Part name Q’ty Remarks
Disassembling the main axle
Remove the parts in the order below.
1
Reverse pinion gear 1
2
4th pinion gear 1
3
2nd/3rd pinion gear 1
4
Circlip 1
Refer to “ASSEMBLING THE MAIN 
AXLE AND DRIVE AXLE”.
5
Toothed washer 1
6
5th pinion gear 1
7
Main axle/1st pinion gear 1
For assembly, reverse the disassembly
procedure. 

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ENGTRANSMISSION
DRIVE AXLE
Order Job name/Part name Q’ty Remarks
Disassembling the drive axle
Remove the parts in the order below.
1
Washer 1
2
1st wheel gear 1
3
5th wheel gear 1
4
Circlip 3
Refer to “ASSEMBLING THE MAIN 
AXLE AND DRIVE AXLE”.
5
Toothed washer 3
6
3rd wheel gear 1
7
Toothed collar 2
8
Toothed lock washer 1
9
Toothed lock washer retainer 1
0
2nd wheel gear 1 

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ENGTRANSMISSION
Order Job name/Part name Q’ty Remarks
A
4th wheel gear 1
B
Reverse wheel gear 1
C
Collar 1
D
Drive axle 1
For assembly, reverse the disassembly
procedure. 

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ENGTRANSMISSION
CHECKING THE SHIFT FORK
1.Check:

Shift fork cam follower 1
 

Shift fork pawl 2
 
Scoring/bends/wear/damage →
 Replace.
2.Check:

Guide bar
Roll the guide bar on a flat surface.
Bends →
 Replace.
WARNING
Do not attempt to straighten a bent guide
bar.
3.Check:

Shift fork movement
(on the guide bar)
Unsmooth operation →
 Replace the shift fork
and the guide bar as a set.
CHECKING THE SHIFT DRUM
1.Check:

Shift cam grooves
Scratches/wear/damage →
 Replace.
CHECKING THE TRANSMISSION...

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ENGTRANSMISSION
2.Measure:

Drive axle runout
(with a centering device and dial gauge 1
)
Out of specification →
 Replace the drive axle.
Maximum drive axle runout:
0.08 mm (0.0031 in)
3.Check:

Transmission gears
Blue discoloration/pitting/wear →
 Replace
the defective gear(s).

Transmission gear dogs
Cracks/damage/rounded edges →
 Replace
the defective gear(s).
4.Check:

Transmission gear engagement
(each pinion gear to its respective wheel
gear)
Incorrect →
 Reassemble the transmission
axle...

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ENGTRANSMISSION
2.Install:

Reverse pinion gear 1
 
NOTE:
Press the reverse pinion gear into the main
axle 2
, as shown in the illustration.
a115.65 ~ 115.85 mm (4.553 ~ 4.561 in)
INSTALLING THE TRANSMISSION
1.Install:

Shift drum 1
 

Shift fork “L” 2
 

Shift fork “R” 3
 

Shift fork guide bar (long) 4
 

Shift fork “C” 5
 

Shift fork guide bar (short) 6
 
NOTE:
The embossed marks on the shift forks should
face towards the right side of the engine and
be in the following sequence: “R”, “C”,...

6 - 1
COOLRADIATOR
COOLING SYSTEM
RADIATOR
Order Job name/Part name Q’ty Remarks
Removing the radiator
Remove the parts in the order below.
Front panel and front fender Refer to “SEAT, FENDERS AND FUEL 
TANK” in CHAPTER 3.
Coolant Drain.
1 Radiator fan coupler 1 Disconnect.
2 Thermo switch coupler 1 Disconnect.
3 Coolant reservoir hose 1
4 Radiator fan breather hose 1 Disconnect.
5 Radiator outlet hose 1 Disconnect.
6 Radiator inlet hose  1 Disconnect.
7 Radiator 1
8 Radiator fan 1
9 Thermo switch 1 1
10...