Honda SH125 Manual page 357

TROUBLESHOOTING
~~
POOR PERFORMANCE AT HIGH SPEED
1. Ignition Timing Inspection
Check the ignition timing.
Is the ignition timing correct?
NO
-
Faulty engine control module (ECM)
Faulty crankshaft position (CKP) sensor
Improper valve timing
YES
-
GO TO STEP 2.
2. Fuel Injection System Inspection
Check the fuel injection system (page 5-71,
Is the fuel injection system normal?
NO
-
Faulty fuel injection system.
YES
-
GO TO STEP 3.
3. Fuel Line Inspection
Check the fuel line (page 5-31).
Is the fuel line normal?
NO
-
Faulty fuel line or fuel p u m p system.
YES
-
GO TO STEP 4.
4. 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.
5. Air Cleaner Inspection
Check the air cleaner.
Is the air cleaner element clean?
NO
-
Dirty air cleaner
YES
-
GO TO STEP 6.
6. Valve Timing Inspection
Check the valve timing.
Is the valve timing correct?
NO
-
Cam sprocket not installed properly
YES
-
GO TO STEP 7.
7. Camshaft Inspection
Remove and inspect the camshaft.
Is the cam lobe height within specification?
NO
-
Faultycamshaft
YES
-
GO TO STEP 8.
8. Valve Spring Inspection
Check the valve springs.
Are the valve springs normal?
NO
-
Faulty valve springs