John Deere stx38 - Manual (Page 65)

4/23/97
3 - 33
ENGINE REPAIR
REMOVE AND INSTALL VALVES
AND SPRINGS
IMPORTANT: Make sure keepers are seated in
valve stem groove (D).
1. Compress intake and exhaust springs using an
appropriate size spring compressor.
2. Remove keepers (C), spring caps (B), springs (A),
and valves (E).
IMPORTANT: STX38 (SN 210000— ) intake valve
seal is not required.
3. Install valve components.
4. Compress spring and install keepers in grooves
(D).
5. Install rocker arm assembly and cylinder head in
reverse order.
INSPECT CYLINDER HEAD
1. Remove carbon deposits and clean gasket surface
with SCOTCH-BRITE®
1
abrasive or equivalent.
2. Inspect head for cracks or damage. Make sure oil
drain port is open.
1. SCOTCH-BRITE is a registered trademark of the
3M Company.
3. Put head on a flat surface plate. Check for
distortion at several points with a feeler gauge.
Replace head if distorted beyond specification.
Specification:
Cylinder Head Distortion (maximum)
. . . . . . . . . . . . . . . . . . . . . . . . . . 0.076 mm (0.003 in.)
INSPECT VALVES
1. Remove carbon from valve head, face, and stem.
2. Check valve for cracks or damage.
3. Replace warped valves (A) or valves with less than
serviceable margin (B). Valve stem ends (C)
should be square, not worn uneven as shown.
4. Inspect valve stems for bends using V-blocks and
dial indicator. Turn valve slowly and read variation.
Replace if variation is greater than specification.
Specification:
Valve Stem Bend (maximum)
. . . . . . . . . . . . . . . . . . . . . . . . 0.076 mm (0.003 in.)
M55867
A
E
B
C
D
M52080
B
A
C
M38087
M51753