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inspection
FAULT
Broken
cooling
fins
Damaged threads
Binding marks in cylinder wall (particularly
at exhaust pod)
Surface
cylinder wail worn (chiefly at top
coating on
of cylinder)
Binding scratches on piston
Piston ring burnt in as groove
Piston ring worn
Assembly
Check that the piston and cylinder are marked with the
same class designation (see
tion table
Check that the gudgeon pin needle bearing is not dama-
ged or worn. Fit it in the connecting rod and lubricate
with a few drops of two-stroke oil.
Fit
the piston to the connecting-rod.
NOTE: The arrow on the piston crown should point to-
ward the exhaust port.
6:2
Fig. 1:1
and the classifica-
REMEDY
In serious cases - change the cylinder
Repair the threads with Heli-Coll inserts.
Clean the damaged area with One emery cloth to remove
adhering aluminium in the case of deeper binding scrat-
ches the cylinder and piston should be replaced
Change cylinder and piston.
Clean the damaged area carefully with a fine file or emery
cloth. Clean the cylinder carefully as described above
before fitting the piston back in place. In the case of
deeper scratches the piston and possibly the cylinder
should be changed. Before assembly, clean both piston
and cylinder carefully to remove all metal bongs.
Carefully remove the piston ring and clean the groove
with extreme thoroughness before reassembly.
Check the wear by positioning the ring i,7 the lowest pan
of the cylinder. The distance between the ends
piston ring should not exceed 0.6 mm. Also check that the
piston ring has lost none of its springiness.
Use a suitable drift to centre the piston opposite the
needle bearing in the connecting-rod. Slide the gudgeon
pin into position and fit the circlips in place. Check that
they are correctly seated in their grooves by rotating
them with a pair of flat-nosed piers.
Lubricate the piston with a few drops of two-stroke off
Place the cylinder gasket in position on the crankcase.
Position the plastic support in assembly kit No. 502 50
70-01 under the piston.
of
the
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