Sym HD 125 Service Manual page 19

1. GENERAL INFORMATION
B. Engine run sluggish (Speed does not pick up, lack of power)
Check and adjustment
Try gradual acceleration and
check engine speed
Engine speed can be
increased.
Check ignition timing (Using
ignition lamp)
Ignition timing correct
Check cylinder compression
pressure (using compression
pressure gauge)
Compression pressure
correct
Check if carburetor jet is
clogged
No clogged
Remove spark plug
No foul or discoloration
Check if engine over heat
Normal
Continually drive in acceleration
or high speed
No knock
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Fault condition
Engine speed can not be
increased.
Incorrect ignition timing
No compression pressure
Clogged
Fouled and discoloration
Engine overheat
Knock
Probable causes
1.
Air cleaner clogged
2.
Poor fuel supply
3.
Lines in fuel tank evaporation system
clogged
4.
Exhaust pipe clogged
5.
Fuel nozzle clogged in carburetor.
6.
Fuel nozzle clogged in carburetor.
1.
Malfunction of CDI
2.
Malfunction of AC alternator
1.
Cylinder & piston ring worn out
2.
Cylinder gasket leaked
3.
Sand hole in compression parts
4.
Valve deterioration
5.
Seized piston ring
1.
Remove foreign
1.
Remove dirt
2.
Incorrect spark plug heat range
1.
Piston and cylinder worn out
2.
Lean mixture
3.
Poor fuel quality
4.
Too much carbon deposited in
combustion chamber
5.
Ignition timing too advanced
6.
Poor circuit on the cooling system
1.
Too much carbon deposited in
combustion chamber
2.
Lean mixture
3.
Poor fuel quality
4.
Ignition timing too advanced