3
L / M . . 09.96
M 06.00 Piston and cylinder
M 06.10 Air-cooled engines
- 12 - 16 - 17 -
Preparations:
– Detach the cylinder head; see M 07.00.
Dismantling:
– Mark the relative position of the cylinder
and piston and pull off the cylinder.
– Take out the piston pin circlip;
see Fig. 65.
– Press the piston pin out by hand and lift
off the piston.
Inspection / repair:
– Check the cylinder wall for seizure
marks or score-marks.
– Check that the dimensions of the
cylinder are correct; for values, see
Section 4.
– Check the piston for seizure marks or
ring web fractures.
– Check piston ring end gaps; for values,
see Section 4.
Checking piston ring end gaps:
–Pull the piston rings off the piston.
– Place each piston ring in its cylinder
bore and move it to the TDC position of
the piston.
– Clean the piston crown and use it to po-
sition the piston ring at a right-angle to
the cylinder axis.
– Use feeler gauges to measure the
piston ring end gap (where the ends of
the piston ring come together).
– For limit values, see Section 4.
65
Checking cylinder wear and suitability
for further use:
– Repeat the piston ring measuring pro-
cedure with a new piston ring.
– Compare the measurements obtained in
this way with the maximum wear limits;
if these are exceeded, the cylinder
should not be re-used but an oversize
cylinder should be installed instead.
– If the measured values are within the
limits, the cylinder can be used again,
with new piston rings.
In this case, the cylinder wall must be
roughened very slightly with a honing tool,
since the honed finish will have been lar-
gely worn after a lengthy period of opera-
tion. If the cylinder were to be used again
without re-honing (whether the existing
piston rings or new ones were fitted), ex-
cessive oil consumption would
occur and would not drop to the normal
level after a time, since the piston rings
would not be able to match themselves
to the cylinder wall.
To Next Page
Loading...
Need help?
General
