2-139
2
Troubleshooting Engine
(120 cc)
Problem: Engine Will Not Start or is Hard to Start (Compression too Low)
Condition
Remedy
1. Valve clearance out of adjustment
2. Valve guides worn — seated poorly
3. Piston rings worn excessively
4. Cylinder bore worn
5. Spark plug seating poorly
1. Adjust clearance
2. Repair — replace guides
3. Replace rings
4. Replace — rebore cylinder
5. Tighten plug
Problem: Engine Will Not Start or is Hard to Start (No Spark)
Condition
Remedy
1. Spark plug fouled
2. Spark plug wet
3. Magneto defective
4. Ignition coil assembly defective
5. Spark plug cap shorted
1. Clean — replace plug
2. Clean — dry plug
3. Replace magneto
4. Replace ignition coil assembly
5. Replace spark plug cap
Problem: Engine Will Not Start or is Hard to Start (No Fuel Reaching the Carburetor)
Condition
Remedy
1. Gas tank vent obstructed
2. Gas tank shut-off valve obstructed — not
turned completely on
3. Carburetor inlet needle defective
4. Fuel hose obstructed
5. Fuel filter obstructed
1. Clean vent completely on
2. Clean — turn on valve
3. Replace inlet needle
4. Clean hose
5. Clean — replace fuel filter
Problem: Engine Stalls Easily
Condition
Remedy
1. Spark plug fouled
2. Magneto defective
3. Transistorized ignition module defective
4. Carburetor jets obstructed
5. Valve clearance out of adjustment
6. Exhaust plugged
7. Air cleaner plugged
8. Gasoline contaminated
1. Clean plug
2. Replace magneto
3. Replace ignition coil assembly
4. Clean jets
5. Adjust clearance
6. Unplug — replace muffler
7. Clean — replace air filter
8. Drain and replace gasoline
Problem: Engine Noisy (Excessive Valve Chatter)
Condition
Remedy
1. Valve clearance too large
2. Valve spring(s) weak — broken
3. Camshaft worn
4. Rocker arm — rocker arm shaft worn
1. Adjust clearance
2. Replace spring(s)
3. Replace camshaft
4. Replace arm — shaft
Problem: Engine Noisy (Noise Appears to Come from Piston)
Condition
Remedy
1. Piston — cylinder worn
2. Combustion chamber carbon buildup
excessive
3. Piston pin — piston pin bore worn
4. Piston rings — ring groove(s) worn
1. Replace — service piston — cylinder
2. Clean chamber
3. Replace — service pin — bore
4. Replace rings — piston