Troubleshooting - HYOSUNG COMET 125 Service Manual

7-1 SERVICING INFORMATION

TROUBLESHOOTING

ENGINE
Complaint
Engine will not
start, or is hard
to start.
Engine stalls
easily.
Noisy engine.
Symptom and possible causes
Compression too low
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. Starter motor cranks but too slowly.
Plug not sparking
1. Fouled spark plug.
2. Wet spark plug.
3. Defective ignition coil.
4. Open or short circuit in high tension cord.
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.
1. Fouled spark plug.
2. Clogged fuel hose.
3. Clogged jets in carburetor.
4. Valve clearance out of adjustment.
Excessive valve chatter
1. Valve clearance too large.
2. Weakened or broken valve springs.
3. Worn down camshaft.
Noise appears to come from piston
1. Piston or cylinder worn down.
2. Weakened or broken valve springs.
3. Worn down piston pin or piston pin bore.
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.
Noise seems to come from crankshaft
1. Worn or broken bearings.
2. Big-end bearings worn and broken.
3. Thrust clearance too large.
Remedy
Adjust.
Repair or replace.
Adjust.
Replace.
Replace or rebore.
Retighten.
Consult electrical complaints
Clean or replace.
Clean and dry.
Replace.
Replace..
Clean.
Clean or replace.
Replace.
Clean or replace.
Clean.
Clean.
Clean.
Adjust.
Adjust.
Replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Repair or replace.
Replace.
Replace.
Replace.
Replace.
Replace.
Replace.