kxr 50 90 Workshop-manual : Page 118

          8. CYLINDER/PISTON                                                      Mongoose/KXR 90/50

 SERVICE INFORMATION (Mongoose/KXR 50)
 GENERAL INSTRUCTIONS
 · The cylinder head, 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
                   Item                            Standard (mm)              Service Limit (mm)
 Cylinder head warpage                                                                0.10
 Piston O.D.(3mm from bottom of piston             38.96038.965                      38.90
 Cylinder-to- piston clearance                       0.0350.05                       0.10
 Piston pin hole I.D.                              12.00212.008                      12.03
 Piston pin O.D.                                    11.99412.0                       11.98
 Piston-to-piston pin clearance                     0.0020.014                        0.03
 Piston ring end gap (top/second)                    0.100.25                         0.40
 Connecting rod small end I.D.                     17.00517.017                      17.03
 Cylinder bore                                     39.00539.01                       39.05

 TORQUE VALUES
 Cylinder head bolt               0.81.2kg-m
 Spark plug                       1.11.7kg-m

 TROUBLESHOOTING
 Compression too low, hard starting
 or poor performance at low speed                     Abnormal noisy piston
 · Leaking cylinder head gasket                       · Worn cylinder and piston
 · Loose spark plug                                   · Worn piston pin or piston pin hole
 · Worn, stuck or broken piston and piston rings      · Worn connecting rod small end bearing
 · Worn or damaged cylinder and piston
 Compression too high, overheating
 or knocking                                          Abnormal noisy piston rings
 · Excessive carbon build-up in cylinder head         · Worn, stuck or broken piston rings
   or on piston head                                  · Worn or damaged cylinder




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