zing 125 qe Workshop-manual : Page 18

          1. GENERAL INFORMATION                                                                          ZING125

 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 hole
                                  increases              increase sufficiently   Clogged exhaust muffler
                                                                                 Carburetor fuel level too low
                                                                                 Clogged carburetor high speed fuel
 Check ignition timing using                                                     passage
 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 lubricated   Valve train not         Clogged oil cooler
                                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 at                                                    Ignition timing too advanced
 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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