Trouble Shooting
A. No start or difficult to start
1. Ignition System
| Possible Causes |
Inspection and Repair |
| 1. |
Carbon-fouled or worn out spark plug.
|
Clean or replace plug.
|
| 2. |
Gap incorrect or bridged.
|
Gap to 0.5~0.6mm (0.020~0.016").
|
| 3. |
Contact breaker point burned up or worn out.
|
Clean or change points.
|
| 4. |
Point gap incorrect.
|
Set point gap to 0.3~0.4 mm (0.012~0.016").
|
| 5. |
Ignition timing out of adjustment.
|
Set ignition timing.
|
| 6. |
Ignition coil failed.
|
Use electro-tester to measure primary and secondary winding
resistance. Also make a standard coil test.
|
| 7. |
Condenser shorted out.
|
Use electro-tester to check capacity and insulation.
|
| 8. |
Brown or red ignition wires broken or shorted.
|
Turn on main switch. Hit horn and stoplight. No operation means
possible broken wire.
|
| 9. |
Main switch no good.
|
Check main switch.
|
| 10. |
Blown fuse.
|
Replace.
|
| 11. |
Battery discharged or defective.
|
Check specific gravity of each cell with hydrometer.
|
2. Fuel System
| Possible Causes |
Inspection and Repair |
| 1. |
No gas.
|
Disconnect fuel line at carburetor, turn fuel petcock on, check for
fuel flow.
|
| 2. |
Tank cap vent hole plugged.
|
Clean or repair as necessary.
|
| 3. |
Petcock defective.
|
| 4. |
Fuel line plugged.
|
| 5. |
Carburetor not level.
|
Level carburetors.
|
| 6. |
Carb equalizer tube has hole or loose connection.
|
Repair or replace as necessary.
|
3. Cylinder Compression Measure Shows Low Pressure
| Possible Causes |
Inspection and Repair |
| 1. |
Lack of tappet clearance; valve held open.
|
Adjust tappet.
|
| 2. |
Valve timing incorrect.
|
Camshaft improperly installed or cam chain loose.
|
| 3. |
Cylinder head gasket broken.
|
Check for combustion gases blowing out past gasket.
|
| 4. |
Valve seat defective.
|
See Valve Seat Repair Section of Service Manual.
|
| 5. |
Piston ring(s) defective.
|
Too much smoke while riding motorcycle. especially blue smoke
indicating oil burning. See individual wear sections of Service Manual
for inspection methods.
|
| 6. |
Cylinder tapered or out of round.
|
| 7. |
Valve guide(s) worn out.
|
| 8. |
Guide seals bad.
|
B. Poor idle and/or low speed performance
1. Ignition System
| Possible Causes |
Inspection and Repair |
| 1. |
Spark plug fouled or incorrect gap.
|
Clean and gap, or replace if necessary.
|
| 2. |
Contact points bad.
|
Clean and gap, or replace if necessary.
|
| 3. |
Incorrect ignition timing.
|
Reset timing.
|
| 4. |
Weak spark.
|
Check ignition coil and condenser.
|
| 5. |
Partially discharged or defective battery.
|
Weak horn and lights - check fluid level, recharge.
|
2. Fuel System
| Possible Causes |
Inspection and Repair |
| 1. |
Tank cap vent plugged.
|
Clean or repair as necessary.
|
| 2. |
Fuel petcock plugged.
|
| 3. |
Carburetor slow speed system inoperative.
|
| 4. |
Pilot screw out of adjustment or plugged.
|
| 5. |
Carburetor float level incorrect.
|
| 6. |
Starter levers on.
|
| 7. |
Air leak.
|
Manifold equalizer tube cracked, or rubber carburetor manifold
cracked.
|
| 8. |
Carburetor not level.
|
Level carburetors.
|
| 9. |
Equalizer tube has hole or loose connection.
|
Repair or replace as necessary.
|
3. Compression System
| Possible Causes |
Inspection and Repair |
| 1. |
Incorrect tappet clearance.
|
Adjust tappet.
|
| 2. |
Valve timing (camshaft) incorrect.
|
Camshaft improperly installed or cam chain loose.
|
| 3. |
Valve seat leakage.
|
See Valve Seat Repair Section of Service Manual.
|
| 4. |
Valve guide(s) worn out.
|
Repair as necessary.
|
C. Poor mid-range and high speed performance
1. Ignition System
| Possible Causes |
Inspection and Repair |
| 1. |
Spark plug incorrect.
|
Clean and gap to 0.5~0.6mm (0.020~0.024") or change plug if necessary.
|
| 2. |
Advance (or spring) defective.
|
Advance not able to turn, governor weight not pivoting. Check for
correct "retard" to "full advance" position.
|
| 3. |
Ignition timing off.
|
Reset timing.
|
| 4. |
Points set too close.
|
Re-gap to 0.3~0.4mm (0.012~0.016").
|
2. Fuel System
| Possible Causes |
Inspection and Repair |
| 1. |
Butterfly valve not opening completely or in synchronization.
|
Make corrective adjustment.
|
| 2. |
Dirty air filter element.
|
Clean with high pressure air.
|
| 3. |
Carburetor float level incorrect.
|
Measure and change if required.
|
| 4. |
Incorrect main jet size.
|
Remove jet and check stamped size.
|
| 5. |
Incorrect jet needle clip location.
|
Check position of clip in needle.
|
| 6. |
Cracked and leaking vacuum diaphragm.
|
Remove air cleaner and observe vacuum piston operation while running
engine.
|
| 7. |
Carburetor not level.
|
Level carburetors.
|
| 8. |
Choke half on.
|
Check chokes.
|
3. Compression System
| Possible Causes |
Inspection and Repair |
| 1. |
Weak or broken valve spring.
|
Make valve spring tests, replace if weak.
|
| 2. |
Valve timing (camshaft) incorrect.
|
Check cam chain tension.
|
| 3. |
Broken piston rings.
|
Compression abnormal. Replace.
|
D. Engine overheating
1. Ignition System
| Possible Causes |
Inspection and Repair |
| 1. |
Ignition timing too advanced or retarded.
|
Check timing.
|
| 2. |
Malfunctioning governor.
|
Check action of governor rod and pivot weights.
|
| 3. |
Too hot spark plug heat range.
|
Check heat range.
|
2. Fuel System
| Possible Causes |
Inspection and Repair |
| 1. |
Too lean air-fuel mixture.
|
Any jet plugged or too small. Air leak in carburetion intake system.
|
| 2. |
Bad gasoline.
|
Listen for detonation. Check for unusual deposits on spark plug.
|
3. Oil System
| Possible Causes |
Inspection and Repair |
| 1. |
Oil level too low.
|
Check and refill.
|
| 2. |
Oil too thin.
|
Improper weight or too contaminated - change oil.
|
| 3. |
Oil pump defective.
|
Loosen oil delivery line to head and check for oil flow.
|
| 4. |
Oil passage plugged.
|
Disassemble engine. Pour solvent or direct air through oil passages.
|
3. Too Much Blue Exhaust Smoke
| Possible Causes |
Inspection and Repair |
| 1. |
Too much engine oil.
|
Check oil level and drain some if necessary.
|
| 2. |
Breather plugged up.
|
Check and clean if necessary.
|
| 3. |
Cylinder and/or piston rings worn.
|
Make necessary measurements and replace as necessary.
|
| 4. |
Worn or cracked valve guide.
|
Make necessary measurements and replace as necessary.
|
| 5. |
Cracked valve guide seals.
|
Make necessary inspection and replace as necessary.
|
