Exmark 127-9041 - Page 32

Maintenance
4－13
Cylinder Head
1、Remove carbon deposits from the combustion
chamber. Clean off any gasket material from the
cylinder head surface.
2、Check the spark plug hole and valve areas for cracks.
3、Check the cylinder head for warpage with a straight
edge and a feeler gauge as shown.
Service limit
0.002”
Valve Stem OD
Inspect each valve for face irregularities, bending
or abnormal stem wear. Replace the valve if necessary.
Measure and record each valve stem OD.
Standard
Service limit
IN
0.258” – 0.259”
0.255”
EX
0.257” – 0.258”
0.255”
Replace the valves if their OD is smaller than the service limit.
Valve Guide ID
Ream the exhaust valve guide to remove any
carbon deposits before measuring.
Measure and record each valve guide ID.
Standard
Service limit
0.259” – 0.260”
0.262”
Stem –to- Guide Clearance
Subtract each valve stem OD from the corresponding
guide ID to obtain the guide-to-stem clearance.
Standard
Service limit
IN
0.0008” – 0.0019”
0.0050”
EX
0.0015” – 0.0027”
0.0067”
If the stem-to-guide clearance exceeds the service limit, determine if the
new guide with standard dimensions would bring the clearance within
tolerance. If so, replace the guide (or cylinder head ) as necessary and
ream to fit. If the stem-to-guide clearance exceeds the service limit with
new guides, replace the valves as well.
Recondition the valve seat whenever the valve guide is replaced.
STRAIGHT EDGE
FEELER GAUGE