quannon 125 Workshop-manual : Page 69

          7. CYLINDER/PISTON                                                                QUANNON 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
                                                       Standard (mm)            Service Limit (mm)
                          Item
                   I.D.                                52.40052.410                   52.50
                   Warpage                                                            0.05
     Cylinder
                   Cylindricity                                                       0.05
                   True roundness                                                     0.05
                   Ring-to-groove      top             0.0150.050                     0.09
                   clearance           Second          0.0150.050                     0.09
                                       top               0.150.30                     0.50
     Piston,       Ring end gap        Second            0.150.30                     0.50
     piston ring                       Oil side rail      0.20.9                      
                   Piston O.D.                         52.37052.390                   52.30
                   Piston O.D. measuring position               10mm from bottom of skirt
 .                 Piston-to-cylinder clearance        0.0100.040                     0.01
                   Piston pin hole I.D.                15.00015.008                   15.06
 Piston pin O.D                                        14.99415.000                   14.96
 Piston-to-piston pin clearance                        0.0020.014                     0.02
 Connecting rod small end I.D. bore                    15.01615.034                   15.06


 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 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                                  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
                                                       · Incorrectly installed piston




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