3.6
MAINTENANCE
CYLINDER MEASUREMENT
Inspect each cylinder for wear, scratches, or damage. If no
damage is evident, measure the cylinder for taper and out of
round with a telescoping gauge or a dial bore gauge. Measure
the bore 1/2” from the top of the cylinder; in line with the
piston pin and 90_ to the pin to determine if the bore is out of
round. Repeat the measurements at the middle of the cylinder
and the bottom of the cylinder to determine taper or out of
round at the bottom. Use the chart below and record all
measurements.
CYLINDER HONING
The cylinder bore must be de-glazed whenever new piston
rings are installed. A light honing with fine stones removes
only a very small amount of material. A proper crosshatch
pattern is important to provide a surface that will hold oil, and
allow the rings to seat properly. If the crosshatch is too steep,
oil retention will be reduced. A crosshatch angle which is too
shallow will cause ring vibration, poor sealing, and
overheating of the rings due to blow-by and reduced contact
with the cylinder wall. Service life of the pistons and rings
will be greatly reduced.
NOTE: A Nikasil cylinder can be lightly honed with a
soft stone hone but an not be oversized.
Table 3-2: Cylinder Measurement Worksheet
TOP
Tx Ty
MIDDLE
Mx My
BOTTOM
Bx By
Out of round = Tx - Ty and By - Bx
Taper limit = Ty - By and Tx - Bx
Cylinder taper limit is .002”(.051mm)
Max
Cylinder out of round limit is
.002”(.051mm)
Top
Middle
Bottom
Tx
Mx
Bx
Ty
My
By
EXAMPLE OF A CROSS HATCH PATTERN
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