Checking cylinder head distortion (continued), Valve guide replacement – Generac 86640 User Manual
Page 34
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Checking Cylinder Head Distortion (Con
tinued)
Valve Guide Clearance
Use a suitable dial indicator to measure valve stem to
guide clearance. The valve should be moved parallel to the
rocker arm, since most of the wear occurs in this direction.
See Figure 24.
Figure 24. Valve Guide Clearance
Stem to guide clearance:
Maximum limit
0.10 mm (0.0039 in)
Max. allowable deflection
(Dial indicator readirrgi
0.2 mm (0.008 in)
Valve Guide Replacement
If valve guides must be replaced, proceed as follows:
1. Heat the cylinder head to 302‘-320‘ F. (150‘-160' C.) in an
oil bath (Figure 25).
2. Use a press exerting a 2.2 U.S. ton (20 kN) force to remove
valve guides. If a press is not available, use a hammer and a
suitabfe driving tool (Figure 26).
3. Ream the cylinder head's valve guide hole (Figure 27).
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