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7. TROUBLESHOOTING
If the engine shows any sign of malfunction, the cause should be determined immediately
and appropriate countermeasures should be taken to prevent the problem from worsening.
This section describes certain known problems, their possible causes and appropriate
countermeasures. Note, however, that the list of problems presented here is not all. Generally
speaking, since there is the possibility of multiple causes for a single problem, please use your
experience and common sense when deciding on what action to take.
7-1 ENGINE
The following three conditions must be fulfilled for satisfactory engine start.
1. The cylinder filled with a proper fuel-air mixture.
2. Good compression in the cylinder.
3. Good spark, properly timed, to ignite the mixture.
The engine cannot be started unless these three conditions are met. There are also other factors
which make engine start difficult, e.g., a heavy load on the engine when it is about to start at low
speed, and a high back pressure due to a long exhaust pipe.
Problem and possible cause Remedy
Starting difficulties
1. Ignition system problems 1) Spark plug
• Improper spark plug gap
• Insulation defect
• Carbon deposits
Adjust the gap
Replace
Clean
2) Ignition coil
• Insulation defect or discontinuity
• Poor contact or broken wire
Replace
Repair or replace
3) Improper air gap between ignition coil and flywheel Adjust
4) Bad wire harness Replace
2. Fuel system problems 1) No fuel in fuel tank Refill
2) Fuel hose, Return hose and Fuel pump pulse hose
clogged or pinched
Clean or replace
3) Air in fuel lines Check and retighten joints
4) Poor quality gasoline or water in gasoline Replace
5) Throttle body
• Overflow
• Clogged or damaged
• Throttle valve malfunction (does not close fully)
Adjust
Overhaul
Check and adjust
3. Engine core components
problems
1) Insufficient tightening of cylinder head bolts Check and retighten
2) Wearing of piston, piston rings and/or cylinder Repair or replace
3) Improper contact of valve and seat Repair
4) Valve sticking Repair
5) Improper valve clearance Adjust
6) Leakage from intake manifold gasket Retighten; replace gasket
7) Leakage from carburetor gasket Retighten; replace gasket
8) Insufficient tightening of spark plug Retighten
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