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6
40
Cylinder and piston
Larger, harder particles that enter the engine cause serious damage to the underside of
the piston skirt.
Cause:
• Air
fi
lter damaged or missing.
• Parts from the carburettor or intake
system have come loose and entered
the engine.
Service tips
Action:
In severe cases – replace the cylinder.
Repair the threads using Heli-Coil.
Polish the damaged area using a
fi
ne grade emery cloth so
that the coating of aluminium disappears.
With deep seizure score marks the piston and cylinder
should be replaced.
Replace the cylinder and piston.
Carefully polish the damaged area using a
fi
ne
fi
le of
fi
ne
grade emery cloth. Before the piston is re
fi
tted the cylinder
should be polished as above. With deep score marks the
piston and cylinder should be replaced.
Carefully loosen the piston rings and clean the groove well
before re
fi
tting. Carbon deposits in the groove impair the
important heat transfer between the piston and cylinder.
NOTE!
Be careful with the lower edge of the piston ring
groove. If this is damaged, or if carbon deposits
remain, the compression pressure can leak through.
Check the wear on the piston ring by placing it in the lower
part of the cylinder bore.
Position a suitable punch on the bolt head and give a few
sharp knocks with a hammer. If the bolt still does not loosen,
repeat the procedure.
Defect:
Broken cooling
fi
ns, damaged threads or sheared bolts by
the exhaust port.
Extensive damage to the lower part of the
piston’s inlet side.
Bolts much too tight in the aluminium material.
Piston ring burnt in its groove.
The piston shows signs of seizure score marks.
Surface coating in the cylinder bore worn out (primarily at
the top of the cylinder).
Seizure marks in the cylinder bore (especially by the ex-
haust port).
Action:
Fit a new air
fi
lter.
Regular service and inspection.
Содержание 123HD60
Страница 1: ...Workshop manual 123HD60 123HD65X English ...
Страница 2: ......
Страница 26: ...3 24 Fuel system ...
Страница 50: ...7 48 Crankshaft and crankcase ...
Страница 54: ...52 8 List of tools ...
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Страница 58: ...2010W40 115 39 91 26 ...