CYLINDER BLOCK (Cont'd)
Finishing The Cylinder Walls (Cont'd)
Finish the cylinder to within 0.0015 inch (.038 mm) of the oversize diameter. This will leave enough material for the final
step of honing for correct surface finish and pattern. Use a motor driven hone with spring pressure. Use an
RPM of 300-500
and grit sizes 180-200. Use a lubricate mixture of equal parts of kerosene and SAE No. 20 motor oil
CYLINDER HEADS
Cleaning The Cylinder Heads
With the valves installed to protect the valve seats, remove deposits from the combustion chambers and valve heads with
a scraper and a wire brush. Be careful not to damage the cylinder head gasket surface. Remove the valves and clean the
valve guide cleaning
tool. Use cleaning solvent to remove grease and other debris. Clean all the bolt holes. Remove the
valves and clean the valve guide cleaning
tool. Use cleaning solvent to remove grease and other debris. Clean all the bolt
holes. Remove all the deposits from the valves with a fine wire brush
or
buffing wheel.
Checking The Cylinder Heads
Check the cylinder head for cracks and check the gasket surface for debris and scratches.
When a cylinder head is removed because of gasket leaks, check the flat area of the cylinder head gasket surface for correct
specifications.
If necessary to finish the cylinder head gasket surface, do not machine off more than 0.010 inch (0,254 mm).
Check the valve seat with a gauge.
If the wear is more than specifications allow, grind the valve and valve seat. Measure
the valve seat width. Grind the valve seat when the width is not in specification.
Check the valve surface and the edge of the valve head for damage. Check the stem for damage and the end of the valve
stem for wear.
Check the valve stem to valve guide clearance of each valve in its correct valve guide.
Check the springs for the correct pressure at the specified spring lengths. Use tool
(PIN
6513-DD).
Replace any springs
not in specifications.
Check each spring for being round, using a steel square and a flat surface.
Put the spring and square on end on the flat
surface. Move the spring up to the square. Turn the spring and check the space between the top coil of the spring and the
square. The out of round limits are
0.078 inch (1,98 mm).
Follow the same procedure to check new valve springs before installation. Be sure the correct spring is installed. The
springs are color coded.
TAPPETS
Cleaning The Tappets
Clean the tappets
in
cleaning solvent and wipe the tappets with a clean lint free cloth
Checking The Tappets
Check the tappets for wear
or
damage. Check the bottom end of the tappet to make sure that it has a small amount of
convex. Replace tappets that are damaged, worn,
or
if the bottom is not smooth. If the bottom surface is worn flat, it can
be used with the original camshaft only.
Revised Oct. 97
-7B-18-
741,742,743,
743DS Bobcat Loader
Service Manual
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