Service procedures - engine Group 21
26
7
Connect air to 999 6662. Open the valve.
8
Pull out the locking ring on the knob of the reduction valve.
9
Screw in the knob until the pressure reading is 50 kPa. Main-
tain the pressure for one minute.
10
Increase the pressure to 150 kPa. Secure the knob of the
reduction valve by pushing the locking ring down. Shut the
valve on 999 6662.
11
After 2 minutes, check whether the pressure has dropped on
999 6662, or if bubbles of air can be seen in the bath.
12
Remove the air hose from 999 6662.
13
Remove 999 6997 (two) from the cylinder head.
Cylinder head, inspection
Unevenness of the cylinder head face must not exceed 0.02
mm (0.0008"). If the unevenness does exceed the maximum
of 0.02 mm, or if any blow-by marks are observed, the cylin-
der head must be face-ground or replaced. Make sure that
the stud is secure.
IMPORTANT! Replace all rubber seals.
Cylinder head, face-grinding
Special tools: 999 2479, 998 9876
When face-grinding, check surface smoothness with a dial
indicator. Surface finish after grinding must be max 1.6 RA.
The measurement (A) from the face of the valve disc to the
face of the cylinder head must be 0.0–0.4 mm. Should fur-
ther machining of the cylinder head face be required, the
valve seats must be milled down to maintain this measure-
ment.
The cylinder head height after face grinding must not be less
than 134.6 mm.
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