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4-3-8 Cylinder head/valve train
1) Disassembly/reassembly:
(1) Disassemble recoil starter/housing; (2) Disassemble fuel tank;
(3) Disassemble ignition coil, flywheel; (4) Disassemble muffler;
(5) Disassemble air cleaner; (6) Disassemble carburetor;
Finally, disassemble the cylinder head/valve train as shown on the above figure.
)2 :Inspect/ Service/ Repair
(1) Valve stem outside diameter
Inspect the valve stem outside diameter with the micrometer,
if finding out of the standard or service limit, or if visually
inspecting the burn and damaged on the valve face, please replace
with new one.
IN EX
Standard 5.440-5.455mm 5.430-5.445mm
service limit 5.310mm 5.300mm
Bolt M6×12 2
pcs
( )
Bolt M6×80 2 pcs
Loosen and tighten the bolts in
a crisscross pattern ,
Especially when tightening, all
bolts should be tightened
gradually and evenly up to
specified torque.
Torque
: 。
8±2N.m
Cylinder head
cover
Gasket
Lock nut
Bolt
Valve rocker shaft
Rocker
Exhaust
rocker
Crankshaft
Camshaft spindle
Sealing ring
Timing chain guide
Chain
Tensioner
Spring
Pin
Stud M8×109
Stud
M6×105
Spark plug: Clean and adjust
spark plug before installation
Cylinder head :Before installation,
remove any carbon deposits from
the combustion chamber, check
retainer contact and measure
pressure
Gasket
Dowel —A type
( )
Φ10×14
Bolt: Assembly /disassembly:
Turn and tighten the bolts in a
crisscross pattern in 2 or 3 steps.
Torque: 26N.m
Spring retainer
Guide seal
Spring
Exhaust valve Before
installation, remove
carbon deposits and
Intake valve
Don’t interchange with the
exhaust valve in assembling.
Intake mark IN
Exhaust mark EX
Be careful not to damage the
valve stem when installing.