16 ENGINE 125
304552-10
– Pretension the valve spring using the special tool.
Valve spring compressor (59029019000) ( p. 252)
Insert for valve spring lever (90129060000) ( p. 259)
– Mount valve keys. Relax the valve spring.
Info
When mounting the valve keys, check that they are seated correctly; prefer-
ably, fix the valve keys to the valve with a little grease.
– Place shims into the valve spring retainers according to the installation position.
16.4.10 Checking the cylinder head (125 Duke)
304520-10
– Check valve guides 1 with the special tool.
Limit plug gauge (90129026000) ( p. 257)
» If the special tool is easy to insert into the valve guide:
– Change the valve guides and valves.
– Check the sealing area of the spark plug thread and the valve seats for damage and
tearing.
» If there is wear or tearing:
– Change the cylinder head.
304521-10
– Check the sealing area of the cylinder for distortion using a straight edge and the
special tool.
Feeler gauge (59029041100) ( p. 253)
Cylinder/cylinder head - distortion of
sealing area
≤ 0.10 mm (≤ 0.0039 in)
» If the measured value does not equal the specified value:
– Change the cylinder head.
302808-10
– Check sealing seat A of the valves.
Valve - sealing seat width
Intake 0.90… 1.10 mm (0.0354…
0.0433 in)
Valve - sealing seat width
Exhaust 0.90… 1.10 mm (0.0354…
0.0433 in)
» If the measured value does not equal the specified value:
– Machine the valve seat.
– Blow compressed air through all oil holes and check that they are clear.
16.4.11 Checking/measuring the cylinder (125 Duke)
304540-10
– Check the cylinder bearing surface for damage.
» If the cylinder bearing surface is damaged:
– Change the cylinder and piston.
– Measure the cylinder diameter at several places in the X and Y axes using a
micrometer to check for oval wear.
Guideline
Cylinder - bore diameter 58.006… 58.013 mm (2.2837…
2.28397 in)
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