Yanmar 1GM User Manual page 118

112
CHAPTER SIX
Exhaust valve guide
Intake valve guide
results with specifications in Tables 1-3. Worn guides
must be replaced.
6. Test the valve springs under load on a spring tester
(Figure 22). Replace any spring that does not meet the
specification listed in Tables 1-3.
7. Inspect the valve seats. Ifworn or burned, they must be
reconditioned. This is a job for a dealer or machine shop,
although the procedure is described in this chapter.
8. Check each spring on a flat surface with a steel square.
See Figure 23. Slowly revolve the spring 360 0 and note
the space between the top of the coil and the square. If it
exceeds 1.4 mm (0.055 in.) at any point, replace the
spring.
9. Check the valve guides for wear and looseness. Refer
to Tables 1-3 for valve guide specifications. A loose valve
guide must be replaced.
Valve Guide Replacement
The cylinder head is equipped with replaceable valve
guides. The intake and exhaust valve guides are different
in shape. Refer to Figure 24. The intake valve guide has a
straight inside bore, while the exhaust valve guide has a
stepped opening at the lower end of the guide.
Take the cylinder head to a dealership or machine shop
if valve guide replacement is required.
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