50 - English
Repair Instructions
Check the following:
• That the cylinder’s surface coating is not worn.
Especially the upper part of the cylinder.
• That the cylinder does not have any chafe or
cutting marks. See gure 60.
• That the piston is free of score marks. Minor
scratches can be polished off using ne emery
paper.
• That the piston ring is not burnt into its groove.
• Measure the wear on the piston rings. This
must not exceed 1 mm. See gure 61. Use the
piston to push the piston ring downward.
• That the gudgeon pin bearing is intact.
• That the intake bellows is intact.
Fig 61
Faults and causes
See Figure 62.
Score marks on the piston (A)
1 Leakage, check not carried out.
2 Too low octane fuel.
3 Too low or incorrect oil in the fuel.
Carbon build-up (B)
1 Too much or incorrect oil in the fuel.
Piston ring breakage
1 Piston ring worn out.
2 Oversized piston ring groove.
Fig 62
Fig 60
Cleaning and inspection of the cylinder
Clean all components, scrape off all gasket re-
mains and soot from the following areas:
• Piston crown
• Top of the cylinder bore (inside)
• Cylinder exhaust port
• Base of the cylinder and/or crankcase
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