mxu 250 300 2 Werkstatthandbuch : Seite 30

          1. GENERAL INFORMATION                                                                               MXU 300/ 250


 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                                                        Coolant level too low
                                                                                  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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