HYOSUNG 2010 ST7 Service Manual page 265

9-9 SERVICING INFORMATION
Complaint
Engine lacks
power.
Engine overheats.
Symptom and possible causes
Defective engine internal / electrical parts
1. Loss of tappet clearance.
2. Weakened valve springs.
3. Valve timing out of adjustment.
4. Worn piston rings or cylinders.
5. Poor seating of valves.
6. Fouled spark plugs.
7. Incorrect spark plugs.
8. Clogged injectors.
9. Defective TP sensor.
10. Clogged air cleaner element.
11. Sucking air from throttle valve or vacuum hose.
12. Too much engine oil.
13. Defective fuel pump or ECU.
14. Defective pick-up coil and ignition coils.
Defective control circuit or sensor
1. Low fuel pressure.
2. Defective TP sensor.
3. Defective IAT sensor.
4. Defective pick-up coil.
5. Defective IAP sensor.
6. Defective ECU.
7. Defective SAV solenoid.
8. Defective GP switch.
Defective engine internal parts
1. Heavy carbon deposit on piston crowns.
2. Not enough oil in the engine.
3. Defective oil pump or clogged oil circuit.
4. Sucking air from intake pipes.
5. Use incorrect engine oil.
6. Defective cooling system.
Lean fuel / air mixture
1. Short-circuited IAP sensor / lead wire.
2. Short-circuited IAT sensor / lead wire.
3. Sucking air from intake pipe joint.
4. Defective fuel injectors.
5. Defective WT sensor.
6. Defective cooling system.
The other factors
1. Ignition timing too advanced due to defective timing advance sys-
tem (WT sensor, pick-up coil, GP switch and ECU).
2. Drive belt / chain is too tight.
Remedy
Adjust.
Replace.
Adjust.
Replace.
Repair.
Clean or replace.
Adjust or replace.
Clean.
Replace.
Clean.
Retighten or replace.
Drain out excess oil.
Replace.
Replace.
Repair or replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Clean.
Add oil.
Replace or clean.
Retighten or replace.
Change.
See radiator section.
Repair or replace.
Repair or replace.
Repair or replace.
Replace.
Replace.
Consult radiator section.
Replace.
Adjust.