KYMCO ZX Service Manual page 23

2
. GENERAL INFORMATION
Check ignition timing
(using a timing light).
Test cylinder
compression (using a
compression gauge)
Check carburetor for
clogging
Remove spark plug and
inspect
Check if engine
overheats
Rapidly accelerate or
run at high speed
POOR PERFORMANCE (ESPECIALLY AT IDLE AND LOW SPEEDS)
Inspection/Adjustment
2-19
Engine speed
increases
Correct timing
Normal
compression
Not Clogged
Plug not fouled or
discolored
Engine does not
overheats
Engine does not
knock
Symptom
Engine speed does
not increase
sufficiently
Incorrect timing
Abnormal
compression
Clogged
Plug fouled or
discolored
Engine overheats
Engine knocks
ZX / SCOUT
• Clogged air cleaner
‚ Clogged fuel filter
ƒ Clogged exhaust muffler
„ Faulty auto bystarter
• Faulty CDI unit
‚ Faulty A.C. generator
• Worn cylinder and piston rings
‚ Blown cylinder head gasket
ƒ Faulty reed valve
• Clogged carburetor jets
• Fouled spark plug
‚ Incorrect heat range plug
• Mixture too lean
‚ Poor quality fuel
ƒ Excessive carbon build-up in
combustion chamber
„ Ignition timing too early
• Excessive carbon build-up in
combustion chamber
‚ Poor quality fuel
ƒ Clutch slipping
„ Mixture too lean
Probable Cause