John Deere stx38 - Manual (Page 77)

4/23/97
3 - 45
ENGINE REPAIR
Middle Compression Ring
(12.5, 13, 14 hp)
. . . . . . . . . . . . 0.040—0.072 mm (0.0016—0.0028 in.)
(15 hp) . . . . . . 0.040—0.085 mm (0.0015—0.0002 in.)
Oil Control Ring
(12.5, 13, 14 hp)
. . . . . . . . . . . . 0.551—0.675 mm (0.0217—0.0266 in.)
(15 hp) . . . . . . 0.176—0.026 mm (0.0069—0.0010 in.)
PISTON ASSEMBLY
MEASUREMENT
NOTE: Connecting rod is available 0.25 mm (0.010
in.) undersize.
1. Tighten cap screws (A) to specification.
2. Measure inside diameter of connecting rod (B).
3. Measure outside diameter of crankshaft journal (C).
4. Determine connecting rod-to-crankshaft clearance.
Replace parts that are not within specifications.
Crankshaft Specifications:
Connecting Rod Journal OD
New . . . . . . 38.958—38.970 mm (1.5338—1.5343 in.)
Wear Limit. . . . . . . . . . . . . . . . 38.94 mm (1.5328 in.)
Taper (maximum) . . . . . . . . . . 0.012 mm (0.0005 in.)
Out-Of-Round (max) . . . . . . . 0.025 mm (0.0010 in.)
Crankshaft-to-Connecting Rod Clearance
New . . . . . . . . 0.030—0.055 mm (0.0012—0.0025 in.)
Wear Limit. . . . . . . . . . . . . . . . . . . (0.07 mm (0.0025)
Connecting Rod Specifications:
Piston Pin End ID
New . . . . 19.015—19.023 mm (0.7486—0.7489 in.)
Wear Limit. . . . . . . . . . . . . 19.036 mm (0.7495 in.)
Piston Pin OD.
New . . . . . 18.995—19.00 mm (0.7478—0.7480 in.)
Wear Limit. . . . . . . . . . . . . (18.994 mm (0.7477 in.)
Connecting Rod Cap Screws Torque
8 mm Straight Shank . . . . . . 22.6 N•m (200 lb-in.)
Step Down Shank. . . . . . . . . 14.6 N•m (130 lb-in.)
6 mm Straight Shank . . . . . . 11.3 N•m (100 lb-in.)
5. Measure diameter of piston at point (D). Point (D) is
6 mm (0.25 in.) from skirt bottom and
perpendicular to piston pin.
Piston Thrust Face OD
12.5, 13, 14 hp
. . . . . . . . . . 86.941—86.959 mm (3.4229—3.4236 in.)
Wear Limit . . . . . . . . . . . . . . . . 86.814 mm (3.4179)
15 hp . . . . . 89.951—89.969 mm (3.5413—3.5420 in.)
Wear Limit . . . . . . . . . . . . . . . . 89.824 mm (3.5363)
6. Measure cylinder bore.
7. Replace piston and/or rebore cylinder block if not
within specifications.
Piston Specifications:
Thrust Face to Cylinder Bore Clearance (New)
12.5, 13, 14 hp
. . . . . . . . . . . . 0.041—0.044 mm (0.0016—0.0017 in.)
15 hp . . . . . . . 0.031—0.043 mm (0.0012—0.0016 in.)
Piston Pin Bore ID.
New . . . . . . 19.006—19.012 mm (0.7483—0.7485 in.)
Wear Limit. . . . . . . . . . . . . . . 19.025 mm (0.7490 in.)
M52112
A
B
C
M52148
D D
M52125