5-9
Disassembling the cylinder head and checking parts for wear
NOTE: the illustration shows the font cylinder. The procedure for the
rear cylinder is identical.
– Pull all of the bucket tappets
1
out of the cylinder head.
NOTE:
– Note down the mounting position to ensure that the same bucket
tappet is inserted in the same bore during installation.
– The compensating washers
2
for the valve clearance (shims) usually
adhere to the bottom of the bucket tappets and should be set aside
together with the bucket tappets.
– Invert the cylinder and cylinder head and remove the three Allen bolts
3
and nuts.
– Remove the cylinder and pistons from the cylinder head and discard
the cylinder head gasket.
– Unscrew the chain guide.
– Press the valve springs together using the valve assembling tool
(590.29.019.000 with the attachment 600.29.041.000
4
) and
remove the valve spring key from the valve shaft. Relieve the springs
and remove from the cylinder head.
NOTE: note down the mounting position of the valves to ensure that the
valves are mounted in the same position during installation.
– Pull the valve shaft seal off the valve shaft with pliers and remove the
valve spring washer.
NOTE: a washer (14x30x2) is located under the spring retainers for the
exhaust valve springs to increase the spring preload.
– Repeat the above procedure for the other valves.
– Clean all parts.
Sealing area
Check the spark plug thread and valve seats for damage or cracks. Use a
straight edge
A
and a feeler gauge
B
to check the sealing area to the
cylinder for distortion. Max. distortion: 0.05 mm.
Valve seats
The valve seats may not be impacted. Width of sealing seat: intake max.
1.40 mm; outlet max. 1.40 mm. Reseat the valves if necessary.
Valves
Check the valve disk for wear and runout. The valve disk runout should
not exceed 0.03 mm. The valve seat may not be impacted. The sealing
area should be in the middle of the valve seat. The valve shaft is hard-
chrome-plated. Wear usually occurs at the valve guide.
Valve guides
The valve guides are checked with the limit plug gauge
C
590.29.026.006 (Ø 6.05 mm). If the limit plug gauge can easily be
pushed into the valve guide, the valve guide needs to be replaced at a
special workshop.
Valve springs
Check the valve springs for fractures or other wear. Measure the spring
length with a sliding caliper in an unloaded condition:
Minimum length of inner spring: 38.0 mm
Maximum length of outer spring: 41.3 mm
1
2
3
3
3
A
B
C
4
