mxu 400 Werkstatthandbuch : Seite 47

                                                          ATV-1069                                                   ATV-1085B
                                                           2. Install the compression rings (1 and 2) so the let-
Measuring Piston Skirt/                                       ter(s) on the top surface of each ring faces the
Cylinder Clearance                                            dome of the piston. Rotate the rings until the ring
                                                              end gaps are on directly opposite sides of the pis-
 1. Measure the cylinder front to back in six places.         ton according to the illustration.
                                                             NOTE: The chrome (silver) ring should be
                                                           installed in the top position.
                                                                                                                       3



                                                 CC397D
 2. Measure the corresponding piston diameter at a
    point 15 mm (0.6 in.) above the piston skirt at a
    right angle to the piston-pin bore. Subtract this                                                       MD1343A

    measurement from the measurement in step 1. The                         ! CAUTION
    difference (clearance) must be within specifica-
    tions.                                                 Incorrect installation of the piston rings will result in
                                                           engine damage.
Installing Piston Rings
                                                           CYLINDER/CYLINDER HEAD
 1. Install ring expander (4) in the bottom groove of      ASSEMBLY
    the piston; then install the thin oil rings (3) over
    the expander making sure the expander ends do           NOTE: If the cylinder/cylinder head assembly
    not overlap. Stagger the end gaps of the upper and
    lower thin oil rings according to the illustration.    cannot be trued, they must be replaced.

  NOTE: Note the direction of the exhaust side of          Cleaning/Inspecting Cylinder Head
the piston (5) for correct ring end gap orientation.
                                                                            ! CAUTION
                                                           The cylinder head studs must be removed for this
                                                           procedure.

                                                           1. Using a non-metallic carbon removal tool, remove
                                                              any carbon buildup from the combustion chamber
                                                              being careful not to nick, scrape, or damage the
                                                              combustion chamber or the sealing surface.
                                                           2. Inspect the spark plug hole for any damaged
                                                              threads. Repair damaged threads using a
                                                              "heli-coil" insert.

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