FUSO 4M4 – Engine – CYLINDER HEAD AND VALVE MECHANISM – Installation procedure

Installation: Connecting rod bearings

• Select and use a bearing set of a thickness that can accommodate the inside diameter of the connecting rod’s large end and the diameter of the crankshaft pin. Use either of the following methods for the selection.
(1) Measurement based selection
• Install the connecting rod cap on the piston and connecting rod assembly without fitting the lower and upper bearings.
• Tighten the nut to 49 N·m {5.0 kgf· m}.
• Measure the inside diameter of the connecting rod’s large end (vertically from one point), and the outside diameter of the crankshaft pin (vertically or horizontally from one point).

• Select a bearing set that matches the measurements from the table below.
If the color identification mark is indiscernible, measure the thickness of the bearing walls and use the measurements in its place.

(2) Color identification mark based method
• Use selection by identification color for new parts.
• The connecting rods, crankshafts, and bearings can be appropriately combined in the following ways according to their color identification marks:

Each crankshaft also has an identification mark (“1” or “2”) indicating the diameter of each pin.

Installation: Piston and connecting rod

•Check that the piston ring end gaps are in their correct positions.
A: 1st compression ring end gap
B: 2nd compression ring end gap
C: Oil ring end gap
D: Oil ring expander spring end gap Front mark on piston: “o ”

• If the cylinder has not been machined to an oversize, check that the size marks (“A”, “B” or “C”) on the piston and the upper crankcase are the same.
• Cover the connecting rod bolts with vinyl hoses to prevent them from scratching the wall surface of the cylinder in the upper crankcase and the crankshaft pin.

• Face the front mark “ ” of the piston toward the front of the engine and install the piston.

• After installing the piston and connecting rod assembly, align the mating marks on the connecting rod and connecting rod cap and tighten the nuts alternately in the following manner.
• Tighten the nut to a torque of 49 N·m {5.0 kgf·m}.
• After tightening, tighten the nut further by 90 degrees to the right. Put a punch mark on the nut’s top surface to indicate the number of times it has been used.


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