Engine Run Sluggish (Speed Does Not Pick Up, Lack Of Power) - Sym JET 4 R 50 Series Service Manual

1. GENERAL INFORMATION/TROUBLE DIAGNOSIS
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
1-10
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
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. Crankcase leakage for
pre-compression
1. Remove dirt
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
1. Too much carbon deposited in
combustion chamber
2. Lean mixture
3. Poor fuel quality
4. Lean mixture