Service Manual

Oversized Pistons, Cylinder Bore and Rings (Fig. 73, 74, 75)

1. Check the piston for wear, signs of seizure or nicks.

Replace it if it is defective.

2. Measure the piston outside diameter. If the clearance

between the piston and the cylinder exceeds 0.01 18 in.

(.3 mm), replace the piston.

NOTE: The piston O.D. should be measured at the

wer end of the skirt across the thrust faces, or on

access points perpendicular to the piston pin direction.

3. Thoroughly clean the carbon deposits from the piston

d ring grooves. A ring groove cleaner, or piece of a

discarded ring may be used to clean the ring grooves.

4. Measure the piston ring side clearances using a

ickness gauge.

If the piston ring side clearance exceeds the service limit

in the chart below, the ring must be replaced.

NOTE: In the case of a tapered ring (No. 1), measure

the clearance on the bottom, or widest area of the ring.

Figure 73

Measuring piston outside diameter

Figure 74

Measuring piston ring side clearance

5. Measure the piston ring gap clearance. Insert the ring

into the least worn area of the cylinder by pushing it into

place with the piston. The standard gap is 0.0059 -

0.0157 inch (0.15 - 0.4 mm). If the gap exceeds 0.0590

inch (1.5 mm) the ring must be replaced.

Figure 75

Measuring piston ring gap clearance

Cylinder Block Overhaul Page 4 - 58 Groundsmaster

300 Series