Troubleshooting - HYOSUNG GF125 Service Manual

7-1 SERVICING INFORMA TION

TROUBLESHOOTING

ENGINE
Complaint
Engine will not start or is
Compression too low
hard to start.
1. Valve clearance out of adjustment.
2. Worn valve guides or poor seating of valves.
3. Valves mistiming
4. Piston rings excessively worn.
5. Worn-down cylinder bore.
6. Poor seating of spark plug.
7. Starte motor cranks but too slowly.
Plug not sparking
1. Fouled spark plug.
2. Wet spark plug.
3. Defective pick up coil.
4. Defective CDI unit.
5. Defective ignition coil.
6. Open or short circuit in high tension cord.
7. Open or short circuit of stator coil.
No fuel reaching the carburetor
1. Clogged hole in the fuel tank cap.
2. Clogged or defective fuel cock.
3. Defective carburetor float valve.
4. Clogged fuel pipe.
Engine stalls 1. Foulded spark plug.
easily.
2. Defective pick up coil.
3. Defective C.D.I unit.
4. Clogged fuel pipe.
5. Clogged jets in carburetor.
6. Valve clearance out of adjustment.
Noisy engine.
Excessive valve chatter
1. Valve clearance too large.
2. Weakened or broken valve springs.
3. Worn down rocker arm or rocker arm shaft.
Noise appears to come from piston
1. Piston or cylinder worn down.
2. Combustion chamber fouled with carbon.
3. Piston pin or piston pin bore worn.
4. Piston rings or ring groove worn.
Noise seems to come from timing chain
1. Stretched chain
2. Worn sprockets.
3. Tension adjuster not working.
Noise seems to come from clutch
1. Worn splines of countershaft or hub.
2. Worn teeth of cluth plates.
3. Distorted clutch plates, driven and drive.
4. Clutch dampers weakened.
Noise seems to come from crankshaft
1. Worn or burnt bearings.
2. Big-end bearings worn and burnt.
3. Thrust clearance too large.
Symptom and possible causes Remedy
Adjust.
Repair or replace.
Adjust.
Replace.
Replace or rebore.
Retighten.
Consult "electrical complaints"
Clean or replace.
Clean and dry.
Replace.
Replace.
Replace.
Replace.
Clean.
Clean or replace.
Replace.
Clean or replace.
Clean.
Replace.
Replace.
Clean.
Clean.
Adjust.
Adjust.
Replace.
Replace.
Replace.
Clean.
Replace.
Replace.
Replace.
Replace.
Repair or replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Replace.