John Deere stx38 - Manual (Page 67)

4/23/97
3 - 35
ENGINE REPAIR
INSPECT VALVE GUIDES
1. Clean inside of valve guide. Standard valve guide
reamer (D20020WI) can be used.
2. Measure inside diameter of guide with gauge (A).
3. Measure outside diameter of valve stem (B).
4. An oversize valve is available. Replace valve if
stem-to-guide clearance is too great.
IMPORTANT: If guide is reamed oversized, an
oversize valve must be installed.
5. Use oversize reaming tool (JDG705) to ream guide,
if necessary.
6. Replace cylinder head if inside diameter of guide is
greater than oversize specification.
Specifications:
Valve Guide Ream (standard)
. . . . . . . . . . . . . . . . . . . . . . . . . 7.048 mm (0.2775 in.)
Valve Guide Ream (oversize)
. . . . . . . . . . . . . . . . . . . . . . . . . 7.298 mm (0.2873 in.)
Intake Stem-to-Guide Clearance
. . . . . . . . . . . . . 0.38—0.076 mm (0.0015—0.0030 in.)
Intake Guide (Maximum Wear)
. . . . . . . . . . . . . . . . . . . . . . . . . 7.134 mm (0.2809 in.)
Exhaust Stem-to-Guide Clearance
. . . . . . . . . . . . . 0.050—0.088 mm (0.002—0.0035 in.)
Exhaust Guide (Maximum Wear)
. . . . . . . . . . . . . . . . . . . . . . . . . 7.159 mm (0.2819 in.)
RECONDITION VALVE SEATS
1. Inspect valve seats.
2. Replace cylinder head if seats are warped or
distorted beyond reconditioning.
3. Reface pitted or worn seats as shown in drawing.
4. Lap valves after refacing
5. Check seat for good contact using Prussian Blue
Compound.
M52081
A
M52082
B
Exhaust Valve
Exhaust Insert
Intake Valve
Intake Insert
89°
6.5
35.63/
45°
1.5
6.982/7.000
89°
89°
45°
7.033/
1.5
37.987/
38.013
34.013/
33.987
7.058
7.033/
7.058
M55939
31.63/
31.37
35.37
6.970/6.988