Sym MB10A7-A series Service Manual page 19

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1. General Information
C. Engine runs sluggish (especially in low speed and idling)
Check and adjustment
Check ignition timing
(Using ignition lamp)
Normal
Adjust the air screw of
carburetor
Good
Air sucked in through
carburetor gasket
No air sucked in
Remove spark plug, install
spark plug into spark plug
cap and perform spark test
against engine ground
Good spark
1-14
To this chapter contents
Fault condition
Abnormal
Poor
Air sucked in
Poor
Probable causes
1. Incorrect ignition timing (malfunction
of CDI or AC alternator)
1. Rich mixture (loosen the screw)
2. Lean mixture (tighten the screw)
1. Poor heat insulation gasket
2. Carburetor lock loose
3. Poor intake gasket
4. Poor carburetor O-ring
5. Vacuum hose crack
1. Spark plug fouled
2. Malfunction of CDI
3. Malfunction of AC generator
4. Malfunction of ignition coil
5. Open or short circuit in spark plug
leads
6. Malfunction of main switch