Yamaha LB2 1978 - Chapter 7. Appendices; Troubleshooting Guide

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CHAPTER 7. APPENDICES
7-1. TROUBLESHOOTING GUIDE
The following guide is not complete in itself. If a problem is found
within an individual component mentioned in the chart, refer to the
section or chapter involved for inspection procedures.
1. Will not start or difficult to start
a. Ignition system
Possible caus.e
No spark
Weak
or irregular spark
b. Air/Fuel systems
Possible cause
No fuel
Irregular
or poor fuel flow
Bad fuel
Blocked air intake or malfunction
Remedy
1.
Check ignition main switch.
2.
Check points assembly.
3. Check condenser.
4. Check wiring magneto coil.
5. Check ignition coil.
6. Check high tension lead.
7. Check spark plug.
8. Check ignition timing.
1.
Use Electro Tester, spark gap test.
2. Check spark plug.
3.
Check high tension lead.
4. Check ignition assembly.
Remedy
1.
Check fuel tank.
2. Check petcock.
3. Remove fuel pipe, check fuel flow
1. Clean fuel tank, check cap vent.
2. Clean petcock.
3. Remove carburetor, service.
1.
Flush fuel system completely.
2. Add fresh fuel, proper grade.
1.
Clean and fuel filter.
2.
Check reed valve assembly.
c. Engine/Exhaust systems
Possible cause
Remedy
lnc-0rrect compression pressure 1.
If compression is too high, check
for excessive carbon buildup.
2. No compression or low compression
check:
a.
Cylinder head gasket.
b.
Cylinder base gasket.
c. Piston, rings,
cylinder.
Poor bottom end compression
Check crankcase seals, left and right.
Blocked
exhaust system
1.
Check muffler/spark arrester.
2.
Check exhaust port carbon
formation.
3.
Check exhaust pipe for internal
damage.
2. Poor idle and/or low speed performance
a. Ignition system
Possible cause
Remedy
Fouled spark plug or incorrect gap Clean and gap, or replace if necessary.
Improper
contact points
Clean and gap, or replace if necessary.
incorrect ignition timing
Reset timing.
Weak spark
Check ignition coil and condenser.
b. Air/Fuel systems
Possible cause Remedy
Tank cap vent plugged
Clean or repair as necessary.
Fuel petcock plugged
Clean or repair as necessary.
Carburetor slow speed system
Clean or repair as necessary.
inoperative
Pilot screw incorrectly adjusted or plugged Adjust or clean as necessary.
Carburetor
float level incorrect Measure and adjust as required.
Starter lever on Push lever off.
Air leak Repair.
Carburetor
not level Level.
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