This instruction show you guide on how to assemble and do service procedures for Yanmar SMViO45-5 ViO55-5 engine cylinder head.
2) Disassembly Procedure :
Disassemble in the order of the numbers shown in the illustration.
1 Remove the alternator ass’y. (Point 1)
2 Remove the fan, pulley and V belt.
3 Remove the thermostat case. (Point 2)
4 Remove the fuel filter and fuel oil piping. (Point 3)
5 Remove the oil level gage ass’y.
6 Remove the oil filter. (Point 4)
7 Remove the fuel injection pipes. (Point 5)
8 Remove the intake manifold ass’y.
9 Remove the exhaust manifold ass’y.
10 Remove the rocker arm cover ass’y. (Point 6)
11 Remove the rocker shaft ass’y, push rods and valve caps. (Point 7)
12 Remove the cylinder head ass’y and head gasket. (Point 8)
13 Remove the fuel injection valves and fuel return pipe. (Point 9)
14 Remove the intake/exhaust valves, stem seals and valve springs.
15 Remove the rocker arms from the rocker shaft.
3) Reassembly Procedure :
Reverse order of the disassembly procedure.
4) Servicing Points
• Loosen the mounting bolt while supporting the alternator.
Do not tilt the alternator toward the cylinder block in a haste since it may damage the alternator or pinch a finger.
• The belt deflection shall be 0.39 to 0.59 in. (10 to 15 mm) (0.28 to 0.35 in. (7 to 9 mm)) for a new belt).
• Replace the belt with a new one if cracked, worn or damaged.
• Carefully prevent the belt from being smeared with oil or grease.
• Check the thermostat function.
• Replace the fuel filter element with a new one.
• Cover the fuel pipe opening with tape to prevent intrusion of foreign matters.
• Replace the oil filter with a new one.
• After fully tightening the filter manually, retighten it with a filter wrench by 3/4 turn.
• Cover the fuel injection pipe and pump inlets and outlets with tape or the like to prevent intrusion of foreign matters.
Breather system (A redactor to intake air system of blowby gas)
Emitting blowby gas is harmful to natural environment. Therefore blowby gas redactor is adopted to the engine. Some of the combustion gas passes through the clearance between the cylinder and the piston, piston ring, and flows to the crankcase.
This is said as blowby gas. While it passes into the cylinder head and the rocker arm cover, the blowby gas mixes with splash oil, and becomes oil mist-blowby gas mixes with splash
oil, and becomes oil mist-blowby gas it passing through the baffle plate inside a rocker arm cover. And it passes through a diaphragm assy, and a intake manifold, and is reduced in the
combustion chamber. Pressure inside a crankcase is controlled by the function of the diaphragm assy, and suitable amount of blowby gas is reduced in intake air system.
• When a rocker arm cover is taken off, check whether oil or the like enter the diaphragm space from a small hole on the side of a diaphragm cover or not without disassembling the diaphragm.
• When a diaphragm is damaged, pressure control inside the crankcase becomes insufficient, and troubles occur.
When the internal pressure of the crankcase decreases too much due to the damage of a spring, much blowby gas containing oil is reduced in intake air system, and it may cause the combustion defect by the early dirt of the intake valve or the urgent rotation of the engine by the oil burning.
When pressure progresses in the crank case too much due to the wrong operation of the diaphragm and so on, it is considered that oil leakage from the joint of a oil pan, a oil seal and so on will occur. When a diaphragm is damaged, blowby is discharged from the breathing hole on the side of diaphragm cover, and not reduced in the intake manifold. Therefore, be careful of the diaphragm trouble.
• At lubricating oil replacement or lube oil supply
The amount of lubricating oil isn’t to be beyond the standard upper limit (in the engine horizontally, the upper limit mark of the dip stick). Since the blowby gas redactor is adopted, be careful that the amount of oil mist may be inducted in the combustion chamber and the oil hammer sometimes may occur, when the lubricating oil quantity is beyond the upper limit or an engine is operated beyond the allowable maximum angle of an engine.
• Replace the diaphragm with new one, when it is damaged.
• Keep the removed push rods by attaching tags showing corresponding cylinder Nos.
• Always apply oil to the contact portions of the push rods and valve clearance adjusting screws.
• Loosen the cylinder head bolts in two steps in the illustrated order.
• Place the cylinder head ass’y on a paper board to prevent the combustion face from any damage.
• Remove the head gasket with a new one.
• Uniformly install the head bolts manually after applying oil on the threaded and seat portions.
• They shall be tightened in two steps in the reverse of the order for disassembly.
First step : T = 31.0 to 34.0 ft•lbf. (41.1 to 46.9 N•m)
Second step : T = 63.0 to 67.0 ft•lbf. (85.3 to 91.1 N•m)
• Carefully remove the fuel injection valve so as not to leave the tip end protector from being left inside the cylinder.
• Replace the fuel injection valve protector with a new one.
• When removing each intake/exhaust valve from the cylinder head, use a valve spring compressor and compress the valve spring and remove the valve cotter.
• Keep each removed intake/exhaust valve after attaching a tag showing the corresponding cylinder No.
• If cotter burr is seen at the shaft of each intake/exhaust valve stem, remove it with an oilstone and extract the valve from the cylinder head.
• Replace the stem seal with a new one when an intake/exhaust valve is disassembled.
• Carefully install each valve after oil application so as not to damage the stem seal.
• Different stem seals are provided for the intake and exhaust valves. Do not confuse them since those for exhaust valves are marked with yellow paint.
• After assembling the intake/exhaust valve, stem seal, valve spring, seat, and cotter, tap the head of the valve stem lightly for settling.
• Do not forget to install the valve cap.
5) Parts Inspection and Measurement
(1) Cylinder head
Clean the cylinder head, mainly the combustion surface, valve seats and intake/exhaust ports, remove carbon deposit and bonding agent, and check the surface state.
 Appearance check
Check mainly discoloration and crack.
If crack is suspected, perform color check.
 Combustion surface distortion
Apply a strait-edge in two diagonal directions and on four sides of the cylinder head, and measure distortion with a thickness gage
 Seat contact
Apply a thin coat of minium on the valve seat. Insert the valve in the cylinder and push it against the seat to check seat contact.
Standard : Continuous contact all around
(2) Valve guide
Mainly check damage and wear on the inside wall. Apply
supply part code 129907-11810 when replacing the part.
 Inside diameter
(3) Intake/exhaust valve
Mainly clean and check damage and wear at the valve
stem and seat.
 Seat contact : See (1)  above.
 Stem outside diameter : See (2)  above.
 Valve head thickness
6) Valve Seat Correction
Always check the oil clearance between the valve and valve guide before correcting the valve seat. If it exceeds the
limit, replace the valve or valve guide first to make the clearance satisfy the standard. After correction, wash the
valve and the cylinder head sufficiently with diesel oil to remove all grinding power or compound.
7) Valve Guide Replacement
8) Valve Stem Seal Replacement
Always use a new seal after the intake/exhaust valve is disassembled. Since the one for the exhaust valve is marked with yellow paint, do not confuse the intake and exhaust valves.
 Apply engine oil to the lip.
 Push with the inserting tool for installation.
 Measure and check the projection of valve stem seal to keep
proper clearance between valve guide and stem seal.
Stem seal projection : 0.736 to 0.748 in. (18.7 to 19.0 mm)