John Deere stx38 - Manual (Page 83)

4/23/97
3 - 51
ENGINE REPAIR
CYLINDER BLOCK REMOVE &
INSTALL
All components must be removed from block before
inspection or machine work can be performed.
CYLINDER BLOCK INSPECT
1. Clean and check block for cracks.
2. Cracks not visible to the eye may be detected by
coating the suspected area with mixture of 25
percent kerosene and 75 percent light engine oil.
3. Wipe area dry and immediately apply coating of
zinc oxide dissolved in wood alcohol. If crack is
present, coating becomes discolored at the
defective area.
4. Replace block if any cracks are found.
5. Measure cylinder bore inside diameter at six
places; two measurements 90° apart at top,
middle, and bottom of ring travel.
6. Measure piston outside diameter perpendicular to
piston pin bore.
NOTE: Pistons and rings are available 0.25 and 0.50
mm (0.010 and 0.020 in.) oversize.
Replace block or bore cylinder to accept larger piston if
clearance exceeds specification.
Cylinder Bore Specifications:
12.5, 13, 14 hp
New . . . . 87.000—87.025 mm (3.4252—3.4262 in.)
Wear Limit. . . . . . . . . . . . . 87.063 mm (3.4277 in.)
15 hp
New . . . . 90.000—90.025 mm (3.5433—3.5443 in.)
Wear Limit . . . . . . . . . . . . . . 90.63 mm (3.5681 in.)
Out-of-Round (maximum) . . 0.12 mm (0.0047 in.)
Taper (maximum) . . . . . . . . . 0.05 mm (0.0020 in.)
Piston-to-Cylinder Clearance
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.)
CYLINDER BORE DEGLAZING
IMPORTANT: Remove crankshaft and internal
engine components when deglazing cylinder.
Abrasives can cause engine damage.
1. Use the appropriate size flex-hone to deglaze
cylinder bore.
2. Deglaze cylinder bore using flex-hone to obtain
23—33° crosshatch pattern.
3. Clean abrasive residue from cylinder using warm
soapy water until clean white rags show no
discoloration.
4. Dry cylinder and apply engine oil.
Specification:
Deglaze Crosshatch Pattern . . . . . . . . . . . . . 23—33°
M52133
M52125
M58336