YG125-30B
Maintenance Manual
Cylinder Head, Cylinder and Piston
55
Troubleshooting
l
Low cylinder pressure
1.
Valve:
--
Incorrect valve clearance adjusted;
--
Valve ablated or bent;
--
Valve sealing failure;
--
Incorrect valve timing;
--
Valve spring damaged.
2.
Cylinder head:
--
Spark plug sealing failure;
--
Cylinder head gasket leaked or damaged;
--
Cylinder head cracked or blistered.
3.
Cylinder and piston:
--
Piston ring clearance too big or cracked;
--
Piston cracked or damaged;
--
Cylinder / piston ring worn.
l
Black smoke from exhaust
1.
Valve guide worn;
2.
Oil shield leaked or damaged;
3.
Cylinder / piston / piston ring worn;
4.
Piston ring clearance too big;
5.
Piston ring incorrectly installed;
6.
Piston or cylinder wall scratched or scuffed.
●
Excessive noise
1.
Incorrect valve adjustment;
2.
Valve jammed or valve spring broken;
3.
Camshaft worn or damaged;
4.
Timing chain too long, worn or damaged;
5.
Timing chain tensioned failure;
6.
Timing driven sprocket worn;
7.
Cylinder / piston worn;
8.
Rocker arm / Rocker-arm shaft worn;
9.
Piston pin bore / piston pin worn.
l
Overheat / knocking (cylinder pressure too high)
1.
Too much carbon deposited in combustion
chamber.
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...
