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1. GENERAL INFORMATION Mongoose/KXR 90/50
ENGINE LACKS POWER
Inspection/Adjustment Symptom Probable Cause
Start engine and
accelerate lightly for
observation Clogged air cleaner
Engine speed Engine speed does not Restricted fuel flow
increases increase sufficiently Clogged fuel tank cap breather hole
Clogged exhaust muffler
Check ignition timing Carburetor fuel level too low
(using a timing light)
Faulty ignition unit
Correct timing Incorrect timing
Faulty pulser coil
Check valve clearance
Improper valve clearance
Correct Incorrect adjustment
Excessively worn valve seat
(protruded valve stem)
Test cylinder compression
Improper valve and seat contact
Normal Abnormal Worn cylinder and piston rings
compression compression Leaking cylinder head gasket
Improper valve timing
Check carburetor for
clogging
Not clogged Clogged Clean and unclog
Remove spark plug and
inspect
Plug not fouled or Plug fouled or Fouled spark plug
discolored discolored Incorrect heat range plug
Remove oil dipstick and
check oil level and condition
Incorrect or Oil level too high
Correct and not Oil level too low
contaminated contaminated
Oil not changed
Remove cylinder head oil
pipe bolt and inspect
Valve train not Clogged oil line
Valve train lubricated
properly lubricated properly Faulty oil pump
Check if engine overheats
Worn cylinder and piston rings
Mixture too lean
Engine does not Engine overheats Poor quality fuel
overheats Excessive carbon build-up in
combustion chamber
Ignition timing too early
Rapidly accelerate or run
at high speed
Excessive carbon build-up in
combustion chamber
Engine does not knock Engine knocks Poor quality fuel
Clutch slipping
Mixture too lean
Ignition timing too early
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