vitality 50 2t 4t 1 Manuel atelier : Page 109

          7. CYLINDER HEAD (2-STROKE)/
   CYLINDER/PISTON                                                             VITALITY 50

 SERVICE INFORMATION (4-STROKE)
 GENERAL INSTRUCTIONS
 · The cylinder and piston can be serviced with the engine installed in the frame.
 · Before disassembly, clean the engine to prevent dust from entering the engine.
 · Remove all gasket material from the mating surfaces.
 · Do not use a driver to pry between the cylinder and cylinder head, cylinder and crankcase.
 · Do not damage the cylinder inside and the piston surface.
 · After disassembly, clean the removed parts before inspection. When assembling, apply the
   specified engine oil to movable parts.

 SPECIFICATIONS
                                                      Standard (mm)         Service Limit (mm)
                I.D.                                   39.0039.01                   39.1
                Warpage                                                            0.05
  Cylinder
                Cylindricity                                                       0.05
                True roundness                                                     0.05
                Ring-to-groove Top                     0.0150.055                   0.09
                clearance         Second               0.0150.055                   0.09
                                  Top                    0.150.3                    0.5
  Piston,       Ring end gap      Second                 0.30.45                    0.65
  piston ring                     Oil ring                0.20.7                    0.9
                Piston O.D.                           38.97538.99                   38.9
                Piston O.D. measuring position   4.5mm from bottom of skirt          
 .              Piston-to-cylinder clearance          0.0100.040                     0.1
                Piston pin hole I.D.                 13.00213.008                  13.04
  Piston pin O.D                                     12.99413.000                  12.96
  Piston-to-piston pin clearance                      0.0020.014                    0.02
  Connecting rod small end I.D. bore                 13.01613.034                  13.06

 TROUBLESHOOTING
 · When hard starting or poor performance at low speed occurs, check the crankcase breather for
   white smoke. If white smoke is found, it means that the piston rings are worn, stuck or broken.
 Compression too low or uneven
 compression                                        Excessive smoke from exhaust muffler
 · Worn, stuck or broken piston rings               · Worn or damaged piston rings
 · Worn or damaged cylinder and piston              · Worn or damaged cylinder and piston
 Compression too high                               Abnormal noisy piston
 · Excessive carbon build-up in combustion          · Worn cylinder, piston and piston rings
   chamber or on piston head                        · Worn piston pin hole and piston pin




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