YG125-30B
Maintenance Manual
Cylinder Head, Cylinder and Piston
53
Cylinder head, cylinder and piston
Maintenance notice
Cylinder head
Troubleshooting
Cylinder
Cylinder head cover
Piston
Camshaft
Maintenance notice
The lubrication of the camshaft and rocker arm is implemented by pumping oil by the oil pump through the oil troughs of
the cylinder, cylinder head and cylinder head cover; before assembling, please check whether the oil troughs are
unobstructed and clean them up properly.
Before assembling, clean all parts and components with cleaning agent and dry them with compressed air.
While assembling, coat engine oil and molybdenum disulfide lubricant on the protruding surface of the camshaft for
preliminary lubrication.
Be careful not to damage the cylinder wall and piston.
Technical specifications & maintenance benchmark
Item
Standard value
Maintenance limit value
Camshaft
Camshaft lift: IN
5.15mm
5.21mm
Camshaft lift: EX
5.0mm
5.06mm
Cylinder head
Planeness
0.03mm
0.05mm
Valve spring
Internal spring free
length
36.5mm
36mm
External spring free
length
36.5mm
36mm
Valve
IN Valve stem
external diameter
φ
5mm
φ
4.975mm
Conduit inner
diameter
φ
5 mm
φ
5.012mm
EX Valve stem
external diameter
φ
5mm
φ
4.955mm
Conduit inner
diameter:
φ
5mm
φ
5.012mm
Valve clearance
IN
0.06mm
~
0.08mm
/
EX
0.06mm
~
0.08mm
/
Cylinder
Internal diameter
φ
52.4mm
~φ
52.41mm
φ
52.41mm
Roundness
/
0.003
Cylindricity
/
0.004
Summary of Contents for YG125-30B
Page 99: ...YG125 30B Maintenance Manual Frame and exhaust system 106 10 Frame and exhaust system...
Page 130: ...YG125 30B Maintenance Manual Illumination signal system 136 Circuit schematic drawing...
Page 141: ...YG125 30B Maintenance Manual Engine management system 147 Circuit schematic drawing...
Page 151: ...YG125 30B Maintenance Manual Electrical System Diagram 157 19 Electrical System Diagram...