Honda SH125 Manual page 356

TROUBLESHOOTING
POOR PERFORMANCE AT LOW AND IDLE SPEED
1. Spark Plug Inspection
Remove and inspect the spark plug.
Is the spark plug in good condition?
NO
-
Plug not serviced frequently enough
Incorrect spark plug heat range
Incorrect spark plug gap
YES
-
GO
TO STEP
2.
2. ignition Timing inspection
Check the ignition timing.
Is the ignition timing correct?
NO
-
Faulty ECM
Faulty crankshaft position (CKP) sensor
Improper valve timing
YES
-
GO TO STEP 3.
3. Intake Air Leaking Inspection
Check for leaks around the intake manifold.
Does it leak?
YES
-
Loose manifold mounting bolt
Damaged insulator
Damaged O-ring
NO
-
GO TO STEP 4.
4. SparkTest
Perform spark test.
Is the spark good?
NO
-
Faultysparkplug
Fouled spark plug
Faulty ignition system (page 18-4)
Improperly adjusted valve clearance
YES
-
Faulty idle air control (IAC) valve
22-5