GPX NC450 - Troubleshooting and Maintenance Overview; Troubleshooting Common Issues; Maintenance Parameters Summary

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1. Troubleshooting
2. Maintenance Instructions
3. Removal of the cylinder head cover
4. Disassembly of the cylinder head
5. Decomposition of the cylinder head
6. Inspection of valve and valve spring
7. Rocker arm inspection
8. Inspection of cylinder head
9. Assembly of cylinder head
10. Installation of cylinder head
11. Installation of cylinder head cover
Troubleshooting
Maintenance notice
Maintenance parameters of each component
project
Standard value mm
Maintenance limit
mm
Axial clearance between rocker arm and cylinder head
rocker arm
0.05～0.3
0.5
Radial clearance between rocker arm and rocker arm
shaft
0.016～0.045
0.08
valve spring free length
Outside: 39.6 Inside:
37.7
Outside: 39.75 Inside:
36.85
valve clearance
0.06～0.08
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Camshaft base circle runout
0.02
0.04
Low cylinder pressure:
1、 valve
Incorrect valve clearance adjustment
Poor valve seal
Incorrect gas timing
Broken valve spring
2、 cylinder head
The spark plug is not tightly connected to the
cylinder head
Damaged cylinder head gasket
Cracks or blisters in the cylinder head
3、 Cylinders, Pistons, Piston Rings
Excessive or broken piston ring clearance
Cylinder block
Exhaust with black smoke
1、 valve guide wear
2、 Oil shield leaking or damaged
3、 Cylinder head gasket leakage
4、 Excessive piston ring clearance
Heat engine noise is too loud or abnormal
1、 Incorrect valve adjustment
2、 Stuck valve or broken valve spring
3、 Excessive wear on the upper rocker arm
4、 Incorrect gas timing
5. Camshaft wear
6. The pressure relief valve is broken
project
Standard value mm
Maintenance limit
mm
valve
valve stem outer
diameter
intake
φ4.972～φ4.987
φ4.96
exhaust
φ4.96～φ4.975
φ4.94
Valve guide inner
diameter
intake
φ5.005～φ5.015
φ5.035
exhaust
φ5.005～φ5.015
φ5.035
Valve stem and guide
clearance
intake
0.018～0.043
0.07
exhaust
0.35～0.055
0.08
valve seal width
1.5
----
cylinder head
Flatness
0.04
0.05
Valve seat working face width
0.8
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