PISTON AND CYLINDER
40 – English
Fig. 7
Fig. 6
Fig. 4
Fig. 5
Max 1 mm
2. The cylinder is free of score marks.
3. The piston is free of score marks. Smaller scratches
can be polished off with fi ne emery paper.
4. The piston ring is not burnt into its groove.
5. Measure piston ring wear by placing it in the bottom
of the cylinder bore and measuring the gap. See fi g.
4. The piston ring gap should not exceed 1 mm.
6. The needle roller bearing is undamaged.
7. The inlet manifold is undamaged.
8. Pressure test the decompression valve as follows.
See also fi g. 5.
A. Connect tool 531 03 06-23 to the decompression
valve.
B. Pump up the pressure to 80 kPa (0.8 bar).
C. Wait 30 seconds.
D. The pressure should not be less than 60 kPa (0.6
bar).
Score marks on the piston. Fig. 6.
1. Incorrect carburettor settings. Excessive overspeed.
2. Too low octane fuel.
3. Too little or incorrect oil in the fuel.
Carbon build-up. Fig 7.
1. Incorrect carburettor setting. Too low overspeed.
2. Too much or incorrect oil in the fuel.
Piston ring breakage
1. Excessive engine speed.
2. Piston ring worn out.
3. Piston ring grove sloppy.
Faults and causes
