quannon 125 Workshop-manual : Page 18

          1. GENERAL INFORMATION                                                                  QUANNON 125
 POOR PERFORMANCE (ENGINE LACKS POWER)

 Inspection/Adjustment                         Symptom                       Probable Cause
 Start engine and
 accelerate lightly for
 observation                                                               Clogged air cleaner
                                                                           Poor fuel flow (Restricted)
                               Engine speed        Engine speed does not   Clogged fuel tank cap breather
                               increases           increase sufficiently     hole
                                                                           Clogged exhaust muffler
                                                                           Carburetor fuel level too low
                                                                           Clogged carburetor high speed
 Check ignition timing                                                     fuel passage
 using a timing light

                                   Correct               Incorrect         Faulty CDI unit
                                                                           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
 Check crankcase for oil
 level and condition
                               Correct and not         Incorrect or        Oil level too high
                               contaminated            contaminated        Oil level too low
                                                                           Oil not changed
 Remove cylinder head oil
 pipe bolt and inspect

                             Valve train           Valve train not         Clogged oil cooler
                             lubricated properly   lubricated properly     Clogged oil line
                                                                           Faulty oil pump

 Check for engine
 overheating                                                               Worn cylinder and piston rings
                                                                           Mixture too lean
                               Engine does not       Engine overheats      Poor quality fuel
                               overheats                                   Excessive carbon buildup in
                                                                           combustion chamber
 Rapidly accelerate or run                                                 Ignition timing too advanced
 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 advanced

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