Yanmar 3JH4E Service Manual page 116

5. Inspection and Servicing of Basic Engine Parts
(4) Valve guide
1) Measuring inside diameter of valve guide.
Measure the inside diameter of the valve guide and replace it if it exceeds the wear limit.
Intake
Valve guide
inside dia.
Exhaust
Intake
Clearance
Exhaust
NOTE: The inside diameter standard dimensions assume a pressure fit.
2) Replacing the valve guide
Use the insertion tool and tap in the guide with a
mallet.
The intake valve guide and exhaust valve guide
are of different dimensions.
3) Valve guide projection
The valve guide should project 15mm from the top
of the cylinder head.
4) Valve stem seals
The valve stem seals in the intake/exhaust valve
guides cannot be re-used once they are removed
- be sure to replace them.
When assembling the intake/exhaust valves,
apply an adequate quantity of engine oil on the
valve stem before inserting them.
Exhaust stem seal is marked by yellow. Intake
stem seal is not marked.
Standard
Ø8.010-Ø8.025
Ø8.015-Ø8.030
0.035-0.070
0.045-0.075
100
mm
Limit
Ø8.2
Ø8.2
0.18
0.18
Tool
Valve guide
Cylinder head
Projection
Stem seal
Valve guide
Tool
Valve guide