Page 195 of 362
AC MAGNETO................................................................................................ 5-61
REMOVING THE AC MAGNETO............................................................. 5-62
CHECKING THE AC MAGNETO ............................................................. 5-62
CHECKING THE WOODRUFF KEY ........................................................ 5-62
INSTALLING THE AC MAGNETO ........................................................... 5-62
CRANKCASE................................................................................................. 5-64
DISASSEMBLING THE CRANKCASE..................................................... 5-67
REMOVING THE CRANKCASE BEARING ............................................. 5-67
CHECKING THE TIMING CHAIN, TIMING CHAIN GUIDE, OIL
STRAINER .............................................................................................. 5-67
CHECKING THE CRANKCASE ............................................................... 5-68
ASSEMBLING THE CRANKCASE........................................................... 5-68
CRANKSHAFT ASSEMBLY AND BALANCER SHAFT............................... 5-69
REMOVING THE BALANCER SHAFT..................................................... 5-70
REMOVING THE CRANKSHAFT ASSEMBLY ........................................ 5-70
CHECKING THE CRANKSHAFT ASSEMBLY......................................... 5-70
INSTALLING THE CRANKSHAFT ASSEMBLY....................................... 5-71
TRANSMISSION............................................................................................. 5-72
REMOVING THE TRANSMISSION ......................................................... 5-73
CHECKING THE SHIFT FORKS.............................................................. 5-73
CHECKING THE SHIFT DRUM ASSEMBLY ........................................... 5-74
CHECKING THE TRANSMISSION .......................................................... 5-74
INSTALLING THE TRANSMISSION ........................................................ 5-74
Page 212 of 362
CAMSHAFT
5-17
c. If not, replace the tensioner assembly.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EASB111211CHECKING THE DECOMPRESSION SYS-
TEM
1. Check:
• Decompression system
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Check that the decompressor cam “1”
moves smoothly.
b. Check that the decompressor lever pin “2”
projects from the camshaft.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EASB111212
INSTALLING THE CAMSHAFTS
1. Install:
• Exhaust camshaft “1”
• Intake camshaft “2”
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Turn the crankshaft counterclockwise with a
wrench.
TIP
• Apply molybdenum disulfide oil to the cam-
shafts.
• Apply the engine oil on the decompression
system.
• Fill the cylinder head with engine oil up to the
tops “a” of the valve lifters.
b. Align the top dead center (TDC) mark “a” on
the rotor with the alignment mark “b” on the
crankcase cover.
c. Fit the timing chain “3” onto both camshaft
sprockets and install the camshafts on the
cylinder head.
1
2
a
aa
b
a
Page 226 of 362
VALVES AND VALVE SPRINGS
5-31
EASB111223CHECKING THE VALVE LIFTERS
1. Check:
• Valve lifter
Damage/scratches Replace the valve lift-
ers and cylinder head.
EASB111224INSTALLING THE VALVES
1. Clean:
• Valve stem end
2. Lubricate:
• Valve stem “1”
• Valve stem seal “2”3. Install:
• Spring seat “1”
• Valve stem seal “2”
•Valve “3”
• Valve spring “4”
• Valve spring retainer “5”
(to the cylinder head)
TIP
• Make sure each valve is installed in its original
place.
• Install the valve springs with the larger pitch
“a” facing up.
4. Install:
• Valve cotter “1”
TIP
Install the valve cotters by compressing the
valve spring with the valve spring compressor
“2” and the valve spring compressor adapter
“3”.
Recommended lubricant
Molybdenum disulfide oil
b. Smaller pitch
Valve spring compressor
90890-04019
YM-04019
Valve spring compressor adapter
22 mm
90890-04108
YM-04108
New
Page 229 of 362
CYLINDER AND PISTON
5-34
EASB111226REMOVING THE PISTON
1. Remove:
• Piston pin clips “1”
• Piston pin “2”
• Piston “3”
ECA13810
NOTICE
Do not use a hammer to drive the piston pin
out.
TIP
• Before removing the piston pin clip, cover the
crankcase opening with a cloth to prevent the
piston pin clip from falling into the crankcase.
• Before removing the piston pin, deburr the
piston pin clip’s groove and the piston pin’s
bore area. If the piston pin groove is deburred
and the piston pin is still difficult to remove,
use the piston pin puller set “4”.
2. Remove:
• Top ring
• 2nd ring
• Oil ring
TIP
When removing a piston ring, open the end gap
with your fingers and lift the opposite end gap
of the piston ring over the piston crown.
EASB111227CHECKING THE CYLINDER AND PISTON
1. Check:
• Piston wall (Sidewall)
• Cylinder wall
Vertical scratches Replace the cylinder,
and replace the piston and piston rings as a
set.
2. Measure:
• Piston-to-cylinder clearance
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Measure the cylinder bore with the cylinder
bore gauge.
TIP
Measure cylinder bore by taking side-to-side
and front-to-back measurements of the cylin-
der. Piston pin puller set
90890-01304
Piston pin puller
YU-01304
1
Bore
97.000–97.010 mm (3.8189–
3.8193 in)
Taper limit
0.050 mm (0.0020 in)
Out of round limit
0.050 mm (0.0020 in)
Cylinder bore = maximum of D
1, D2, D3, D4,
D
5, D6
Taper limit (front-to-back) = maximum differ-
ence between D
1, D3, D5Taper limit (side-to-side) = maximum differ-
ence between D
2, D4, D6
Out of round limit (top) = difference between
D
1, D2Out of round limit (middle) = difference be-
tween D
3, D4Out of round limit (bottom) = difference be-
tween D
5, D6
Page 231 of 362
CYLINDER AND PISTON
5-36
TIP
The oil ring expander’s end gap cannot be
measured. If the oil ring rail’s gap is excessive,
replace all three oil rings.
EASB111229CHECKING THE PISTON PIN
1. Check:
• Piston pin
Blue discoloration/grooves Replace the
piston pin and then check the lubrication
system.
2. Measure:
• Piston pin outside diameter “a”
Out of specification Replace the piston
pin.3. Measure:
• Piston pin bore inside diameter “b”
Out of specification Replace the piston.EASB111230INSTALLING THE PISTON AND CYLINDER
1. Install:
• Oil ring expander “1”
• Lower oil ring rail “2”
• Upper oil ring rail “3”
• 2nd ring “4”
• Top ring “5”
TIP
Be sure to install the piston rings so that the
manufacturer’s marks or numbers face up. Piston ring
Top ring
End gap (installed)
0.20–0.30 mm (0.0079–0.0118 in)
Limit
0.55 mm (0.0217 in)
2nd ring
End gap (installed)
0.35–0.50 mm (0.0138–0.0197 in)
Limit
0.85 mm (0.0335 in)
Oil ring
End gap (installed)
0.20–0.50 mm (0.0079–0.0197 in)
Piston pin outside diameter
17.991–18.000 mm (0.7083–
0.7087 in)
Limit
17.971 mm (0.7075 in)
Piston pin bore inside diameter
18.004–18.015 mm (0.7088–
0.7093 in)
Limit
18.045 mm (0.7104 in)
b
Page 238 of 362
CLUTCH
5-43
2. Check:
• Primary-drive-gear-to-primary-driven-gear
free play
Free play exists Replace the primary
drive and primary driven gears as a set.
EASB111242CHECKING THE PRIMARY DRIVEN GEAR
1. Check:
• Primary driven gear
Damage/wear Replace the primary drive
and primary driven gears as a set.
Excessive noise during operation Re-
place the primary drive and primary driven
gears as a set.
EASB111243INSTALLING THE OIL SEAL
1. Install:
• Oil seal “1”
• Washer “2”
• Circlip “3”
TIP
• Apply is lithium-soap-based grease on the oil
seal lip.
• Install the oil seal in parallel with its manufac-
ture's marks or numbers facing inward.
EASB111244INSTALLING THE RIGHT CRANKCASE
COVER
1. Install:
• Dowel pin “1”
• O-rings “2”
• Collar “3”
• Gasket “4”
TIP
Apply the lithium-soap-based grease on the O-
ring.2. Install:
• Right crankcase cover “1”
• Right crankcase cover bolt “2”
TIP
• Apply the engine oil on the impeller shaft end.
• When installing the crankcase cover onto the
crankcase, make sure that the impeller shaft
end “3” aligns with the balancer end slot “4”.
• Tighten the right crankcase cover bolts in
stages and in a crisscross pattern.
New
New
3
2
1
LS
New
New
Right crankcase cover bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
1
1 4
2
New
New
3
LS
T R..
12
Page 243 of 362
KICKSTATER
5-48
EASB111248REMOVING THE KICK SHAFT ASSEMBLY
1. Remove:
• Kick shaft assembly “1”
TIP
Unhook the torsion spring “2” from the hole “a”
in the crankcase.
EASB111249CHECKING THE KICK SHAFT AND RATCH-
ET WHEEL
1. Check:
• Ratchet wheel “1” smooth movement
Unsmooth movement Replace.
• Kick shaft “2”
Wear/damage Replace the kick shaft as-
sembly.
• Spring “3”
Broken Replace.
EASB111250CHECKING THE KICK GEAR, KICK IDLE
GEAR AND RATCHET WHEEL
1. Check:
• Kick gear “1”
Wear/damage Replace the kick shaft as-
sembly.
• Kick idle gear “2”
• Ratchet wheel “3”
• Gear teeth “a”
• Ratchet teeth “b”
Wear/damage Replace.
EASB111251INSTALLING THE KICK SHAFT ASSEMBLY
1. Install:
• Kick gear “1”
• Washer “2”
• Circlip “3”
• Ratchet wheel “4”
• Spring “5”
• Washer “6”
• Circlip “7”
(to the kick shaft “8”)
TIP
• Apply molybdenum disulfide oil to the inner
circumferences of the kick gear and ratchet
wheel.
• Align the punch mark “a” on the ratchet wheel
with the punch mark “b” on the kick shaft.
2. Install:
• Torsion spring “1”
(to the kick shaft “2”)
TIP
Make sure the stopper “a” of the torsion spring
fits into the hole “b” on the kick shaft.
31
2
a
b
3
12
New
New
Page 252 of 362
OIL PUMP AND BALANCER GEAR
5-57
EASB111265REMOVING THE BALANCER
1. Straighten the lock washer tab.
2. Loosen:
• Balancer nut “1”
• Primary drive gear nut “2”
• Balancer weight gear nut “3”
TIP
Place an aluminum plate “a” between the teeth
of the balancer drive gear “4” and balancer
weight gear “5”.
EASB111266CHECKING THE PRIMARY DRIVE GEAR,
BALANCER SHAFT DRIVE GEAR, AND
BALANCER WEIGHT GEAR
1. Check:
• Primary drive gear “1”
• Balancer shaft drive gear “2”
• Balancer weight gear “3”
Wear/damage Replace.
EASB111267CHECKING THE BALANCER
1. Check:
•Balancer
Crack/damage Replace.
EASB111268CHECKING THE OIL PUMP
1. Check:
• Oil pump drive gear
• Oil pump driven gear
• Oil pump housing
• Oil pump housing cover
Cracks/damage/wear Replace the defec-
tive part(s).
2. Measure:
• Inner-rotor-to-outer-rotor-tip clearance “a”
• Outer-rotor-to-oil-pump-housing clearance
“b”
• Oil-pump-housing-to-inner-rotor-and-outer-
rotor clearance “c”
Out of specification Replace the oil pump.
1
5
4
2
a
43
a
5
