• Put the piston ring in the cylinder and measure the
space with an air gap tool. The space must not be
more than 1 mm.
• Examine the surface of the piston.
Score marks on the pis-
ton (A).
The carburetor is incor-
rectly adjusted. Too high
engine speed
Too low octane fuel.
Incorrect oil mixture in
the fuel.
Carbon buildup (B).
The carburetor is incor-
rectly adjusted.
Incorrect oil mixture in
the fuel.
Piston ring damage.
Too high engine speed.
Piston ring worn out.
Too large piston ring
groove.
• Clean and examine the piston ring groove. It must
not be more than 1.6 mm.
• Examine the piston ring play. It must not be more
than 0.15 mm.
7.12.5 To examine the cylinder
• Make sure that the surface layer of the cylinder is
not worn, especially in the top end of the cylinder.
• Make sure that the cylinder does not have score
marks.
42 - Repair instructions 1108 - 001 - 24.11.2020
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