XII Cylinder Head/Valve 
Preparatory data-----------------12.1      Valve guide replacement-------------12.5   
Fault diagnosis------------------12.2      Valve race fixing and adjustment---12.6   
Cylinder head--------------------12.3      Cylinder head installation------------12.7    
Valve Inspection---------------- 12.4       
12.1 Preparatory Data 
Precautions on Operation 
To ensure sealing between cylinder head and cylinder body, there is a great bolt pretension on the cylinder head. 
Pretension value: 50Nm. 
All the components shall be cleaned before inspection and test, and purged with high-pressure air.   
Function of cylinder head: Cylinder head is used to seal cylinder and form a combustion chamber with piston to 
hold high-temperature and high-pressure fuel gas. It accomplishes air intake and exhausting operation with valve 
mechanism. 
Basic Data                                              Unit:mm 
Item Standard Service Limit 
Cylinder cover flatness  0.03  0.05 
Val ve  
Val v e g u id e  
Valve clearance 
Intake 0.03-0.05  _ 
Exhaust 0.03-0.05  _ 
Valve stem OD   
Intake 4.97-4.98  4.9 
Exhaust 4.96-4.97  4.9 
Valve guide ID   
Intake 5 -5.012  5.1 
Exhaust 5-5.012  5.1 
Clearance between valve stem and valve guide 
Intake 0.02-0.042 0.08 
Exhaust 0.03-0.052  0.10 
Valve race width  Intake/Exhaust 0.7  1.5 
Val v e s p ri n g 
Rocker arm 
Clearance 
Rocker arm shaft OD   
 38.8 37.8 
Intake/Exhaust 11.980-11.988 11.95 
Val ve  
Val v e g u id e  
Rocker arm hole ID    Intake/Exhaust 12-12.012  12.05 
Clearance between rocker arm shaft and rocker arm hole Intake/Exhaust 0.012-0.032  0.08 
Valve clearance  Intake  0.03-0.05  _