John Deere stx38 - Manual (Page 84)

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4/23/97
REPAIR ENGINE
REBORE CYLINDER BLOCK
IMPORTANT: Check stone for wear or damage.
Use correct stone.
NOTE: The cylinder block can only be rebored to use
0.25 and 0.50 mm (0.010 and 0.020 in.)
oversize pistons and rings.
1. Align center of bore to drill press center.
2. Adjust hone so lower end is even with lower end of
cylinder bore.
3. Adjust coarse hone stones until they contact
narrowest point of cylinder.
4. Coat cylinder with honing oil. Hone should turn by
hand. Adjust if too tight.
5. Run drill press at about 250 rpm. Move hone up
and down about 60 times per minute.
6. Stop press and check cylinder diameter several
times during honing.
NOTE: Finish should not be smooth. It should have a
23—33° crosshatch pattern.
7. Remove hone when cylinder is within 0.06 mm
(0.0025 in.) of desired size.
8. Hone with burnishing stones until within 0.013 mm
(0.0005 in.) of desired size.
9. Hone with finish stones (220—280 grit) to final size.
10. Allow cylinder to cool completely; then, measure for
new piston-to-cylinder bore running clearance,
taper, and out-of-round.
IMPORTANT: Do not use solvents to clean cylinder
bore. Solvents will not remove metal particles
produced during honing.
11. Clean cylinder thoroughly using warm soapy water
until clean white cloths show no discoloration.
12. Dry cylinder completely and apply thin coat of
engine oil to appropriate mating surfaces.
Specifications:
Oversize Limits
Initial . . . . . . . . . . . . . . . . . . . . . . 0.25 mm (0.010 in.)
Final. . . . . . . . . . . . . . . . . . . . . . . 0.50 mm (0.020 in.)
Drill Speed . . . . . . . . . . . . . . . . . . . . . . . . . . .250 rpm
Hone Cycles . . . . . . . . . . . . . . . . . . . . . 60 per minute
Bore Crosshatch Pattern. . . . . . . . . . . . . . . . 23—33°
Initial Bore Size—Coarse Stone
. . . . . . . . . . . . . . . . Until within 0.06 mm (0.0025 in.)
of desired bore size
Secondary Bore Size—Burnish Stone
. . . . . . . . . . . . . . . . Until within 0.13 mm (0.0005 in.)
of desired bore size
Final Bore Size—Finish Stone
. . . . . . . . . . . . Using 220—280 grit finishing stones
bore to desired size
M85811