KYMCO 2006 MXU 500 Off-Road Owner's Manual page 219

1
. GENERAL INFORMATION
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
Remove oil dipstick and
check oil level and condition
Remove cylinder head oil
pipe bolt and inspect
Check if engine overheats
Rapidly accelerate or run
at high speed
Symptom
Engine speed
increases
Correct timing
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
Engine speed does not
increase sufficiently
Incorrect timing
Incorrect
Abnormal
compression
Clogged
Plug fouled or
discolored
Incorrect or
contaminated
Valve train not
lubricated properly
Engine overheats
Engine knocks
MXU 500
Probable Cause
Clogged air cleaner
Restricted fuel flow
Clogged fuel tank cap breather hole
Clogged exhaust muffler
Carburetor fuel level too low
Faulty ignition unit
Faulty pulser coil
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
Coolant level too low
Worn cylinder and piston rings
Mixture too lean
Poor quality fuel
Excessive carbon build-up in
combustion chamber
Ignition timing too early
Excessive carbon build-up in
combustion chamber
Poor quality fuel
Clutch slipping
Mixture too lean
Ignition timing too early
1-36