John-deere stx38 User Manual download pdf (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

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John-deere stx38 User Manual Page 84

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