1
. GENERAL INFORMATION
CK 1
POOR PERFORMANCE (ENGINE LACKS POWER)
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 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
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
Start engine and accelerate
lightly for observation
Inspection/Adjustment
Symptom
Probable Cause
Engine speed
increases
Correct
Engine speed does not
increase sufficiently
Incorrect
Check ignition timing
using a timing light
Test cylinder compression
Check carburetor for
clogging
Rapidly accelerate or run
at high speed
Remove spark plug and
inspect
Check for engine overheating
Check valve clearance
Correct
Incorrect
Normal
compression
Low compression
Check crankcase for oil
level and condition
Check cylinder head for oil
lubrication
Engine overheats
Engine does not
overheats
Plug not fouled or
discolored
Plug fouled or
discolored
Correct and not
contaminated
Incorrect or
contaminated
Valve train lubricated
properly
Valve train not
lubricated properly
Engine does not knock
Engine knocks
Not clogged
Clogged
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