Yanmar 1GM User Manual page 119

MULTICYLINDER ENGINES
OIL PICKUP
(2GM, 2GM20, 3GM AND
3GM30 MODELS)
When installing the valve guides, the grooved end must
be toward the top of the cylinder head. The groove must
be flush with the head surface as shown in Figure 25.
PUSH RODS
1. Remove the rocker arms as previously described.
2. Remove the push rods and mark them so they can be
reinstalled in their original positions.
3. Inspect the push rod ends for damage. Maximum al-
lowable runout is 0.03 mm (0.0012 in.).
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4. Reinstall the push rods by reversing the removal pro-
cedure. Adjust valve clearance as described in Chapter
Three.
PISTON/CONNECTING ROD ASSEMBLY
Piston/Connecting Rod Removal
1. Remove the engine as described in this chapter.
2. Place a suitable container under the oil pan and remove
the drain plug. Let the crankcase oil drain, then reinstall
the drain plug.
3. Remove the cylinder head as described in this chapter.
4. Remove the oil pan.
5. On 2GM, 2GM20, 3GM and 3GM30 models-Loosen
the oil pickup jam nut (Figure 26) and remove the oil
pickup.
6. Rotate the crankshaft until the piston is at bottom dead
center. Pack the cylinder bore with clean shop rags. Re-
move the carbon ridge at the top ofthe cylinder bore with
a ridge reamer. These can be rented for use. Vacuum out
the shavings, then remove the shop rags.
7. Rotate the crankshaft until the connecting rod is cen-
tered in the bore. Measure the clearance between the con-
necting rod and the crankshaft journal flange with a flat
feeler gauge (Figure 27). Ifthe clearance exceeds specifi-
cations (Tables 1-3), replace the connecting rod during re-
assembly.
8. Remove the connecting rod bolts. Lift off the cap, to-
gether with the lower bearing insert.
9. Use a wooden hammer handle to push the piston and
connecting rod from the bore.
10. Remove the piston rings with a ring remover (Figure
28).