Poor Performance (Engine Lacks Power) - KYMCO VENOX 250 Service Manual

1
. GENERAL INFORMATION

POOR PERFORMANCE (ENGINE LACKS POWER)

Inspection/Adjustment
Start engine and accelerate
lightly for observation
Check ignition timing
(using a timing light)
Check valve clearance
Test cylinder compression
Check carburetor for
clogging
Remove spark plug and
inspect
Check crankcase for oil
level and condition
Check cylinder head for
oil lubrication
Check for engine overheating
Rapidly accelerate or run
at high speed
1-25
Symptom
Engine speed Engine speed does not
increases
increase sufficiently
Correct
Correct
Normal
compression
Not clogged
Plug not fouled or
discolored
Correct and not
contaminated
Valve train lubricated
properly
Engine does not
overheats
Engine does not knock
Incorrect
Incorrect
Low compression
Clogged
Plug fouled or
discolored
Incorrect or
contaminated
Valve train not
lubricated properly
Engine overheats
Engine knocks
VENOX
Probable Cause
Clogged air cleaner
Poor fuel flow (Restricted)
Clogged fuel tank cap breather hole
Clogged exhaust muffler
Carburetor fuel level too low
Clogged carburetor high speed fuel
passage
Faulty CDI unit
Faulty A.C. generator
Improper valve clearance
adjustment
Excessively worn valve seat
(protruded valve stem)
Improper valve and seat contact
Worn cylinder and piston rings
Leaking cylinder head gasket
Improper valve timing
Clean and unclog
Fouled spark plug
Incorrect heat range plug
Oil level too high
Oil level too low
Oil not changed
Clogged oil line
Faulty oil pump
Worn cylinder and piston rings
Mixture too lean
Poor quality fuel
Excessive carbon buildup in
combustion chamber
Ignition timing too advanced
Excessive carbon build-up in
combustion chamber
Poor quality fuel
Clutch slipping
Mixture too lean
Ignition timing too advanced
250