Exhaust and Intake Valves
Exhaust and intake valvesExhaust and intake valves are the casing type, and an extremely soft steel packing is used between the cylinder head and valve seat to the prevent leakage of gas from the Combustion chamber.
The exhaust valve is the water cooled type.
Part of the cooling water from the cylinder head is used to cool the valve. To improve durability, the seating area between the valve and valve seat is treated with stellite, and the top of the valve is equipped with a valve rotator to enable turning of the valve.
1). The intake valve seating area is also treated with stellite.
2). Forced lubrication is used for the exhaust valve system.
1. Disassembly (exhaust valve)
1). Remove mounting nuts with the proper spanner.
2). Evenly jack up and lift the valve casing with the removal tool.
3). Mount the valve spring tool vertically, without any tilt.
4). Screw in the compression shaft further and remove the valve retainer.
5). Loosen the compression shaft until the valve spring is fully extended, and then remove the valve spring tool.
6). Remove the valve spring holder, spring, valve and valve seat, in the given order.
(Valve rotator disassembly)
If the valve rotator shows a rotation defect, disassembly at the earliest possible opportunity, and replace the defective rotator.
Disassembly can be easily done by removing the rotator stop ring. When reassembling, mount balls and springs in the direction indicated by the mark.
2. Inspection after disassembly
1). Check contact and wear at the seating surface between the valve and valve seat, and reface if necessary.
Standard thickness of the stellite coating is about 2 mm for both the valve and valve seat. If wear is greater than 70 % of this thickness (14 mm), retreat with stellite or replace with new parts. If the valve and valve seat show evidence of blow by, refacing may be ineffective because the blow by area has suffered high temperature fatigue and lacks durability.
So it is best to replace with new parts.
2). Check for wear and corrosion of the valve stem and valve casing guide.
If there are signs of corrosion on the guide, this may caused by sulphuric acid due to over cooling.
Be careful to control cooling water temperature.
3). Check contact between the valve casing and valve seat, and reface if necessary.
4). Check for gas leakage between the valve seat and cylinder head mounting surface.
Long term use may damage the cylinder head mounting surface. Reface if necessary.
Do not machine the valve seat side any more than necessary.
5). Check for contact between the valve retainer and valve stem.
1). Join the valve casing and valve seat, and insert the valve.
2). Face the valve downward, and mount the spring and spring guide.
3). Mount the valve spring tool, and screw in the compression rod until the valve retainer can be inserted.
4). Mount the valve retainer.
5). Remove the valve spring tool.
6). Place the valve casing mounting packing in the cylinder head, and insert the valve casing into the cylinder head.
7). Mount nuts, and tighten with the proper spanner to 30° for exhaust valve casings, and to 60° for intake valve casings.
Tighten nuts by alternating at least twice.
a) when mounting intake valves :
✔️ Apply sufficient lubrication to the valve stem, contact surface between the valve and valve seat, and valve retainer area.
b) when inserting exhaust valve into Cylinder head :
✔️ Because the valve casing and area around the valve seat are exposed to exhaust gas, these parts may be difficult to remove due to deposition of carbon. So we recommend Appling an anti burn coating around the valve seat, and inside the cylinder head.
ex.) ishihara chemical, EMOKON IE-25
Never use ordinal grease.
c) A special ultra soft steel packing is used at intake valve mounting surfaces, so do not use any other type of packing.
Manual book Hanshin 6LH 28G