kpw 125 Manuale-dofficina : Pagina 69

          7. CYLINDER/PISTON                                                                    K-PIPE 125

SERVICE INFORMATION
GENERAL INSTRUCTIONS
· The cylinder and piston can be serviced with the engine installed in the frame.
· When installing the cylinder, use a new cylinder gasket and make sure that the dowel pins are correctly
  installed.
· After disassembly, clean the removed parts and dry them with compressed air before inspection.


SPECIFICATIONS

                                  Item                     Standard Limit (mm)     Service Limit (mm)
                 I.D.                                                                     52.4
                 Warpage                                                                  0.05
   Cylinder
                 Cylindricity                                                             0.05
                 True roundness                                                           0.05
                 Ring-to-groove          Top                                              0.12
                 clearance               Second                                           0.12
                 Ring end gap            Top                     0.10.25                   0.5
                                         Second                  0.10.25                   0.5
    Piston,                              Oil side rail           0.10.25                   0.5
  Piston ring    Piston O.D.                                  51.76551.58                 51.6
                                                           5mm from bottom of      5mm from bottom of
                 Piston O.D. measuring position
                                                                    skirt                 skirt
                 Piston-to-piston pin clearance                0.0050.014                  0.1
                 Piston pin hole I.D.                        13.00213.008                  13.0
 Piston pin O.D                                              12.99412.000                12.944
 Connecting rod small end I.D. bore                          13.01613.027                 13.08


 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 or damaged cylinder and piston rings                · Worn or damaged piston rings
 · Worn, stuck or broken piston rings                       · Worn or damaged cylinder and piston

 Compression too high
 · Excessive carbon build-up in combustion chamber
   or on piston head

 Abnormal noisy piston
 · Worn cylinder, piston and piston rings
 · Worn piston pin hole and piston pin
 · Incorrectly installed piston

7-3