YG125-30A Maintenance Manual
Cylinder Head, Cylinder and Piston
55
Troubleshooting
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.
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.
Overheat / knocking (cylinder pressure too high)
1.
Too much carbon deposited in combustion
chamber.
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