Piston / Cylinder - KTM 450 SX-F Repair Manual

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Piston / Cylinder

NIKASIL COATING ON CYLINDER:
Nikasil is the brand name for a cylinder coating process developed by
the Mahle piston company. The name is derived from the two materials
used in the process - one layer of nickel in which the exceptionally
hard silicon carbite is embedded. The major advantages of the Nikasil
coating include its outstanding heat dissipation and the improved
power output, the insignificant wear and low weight of the cylinder. It
is inexpensive to repair (replace) a worn coating if the cylinder barrel is
not damaged.
– To establish the wear to the cylinder, use a micrometer to measure
the cylinder in the middle of the bearing surface.
– Measure the diameter of the cylinder in the X and the Y-axis to
detect any ovality.
Cylinder diameter
450 SX-F / 450 SXS-F
size I: 97.000 - 97.012 mm
size II: 97.012 - 97.025 mm
NOTE: The cylinder size
1
size on the piston head.
2
– The piston is measured at the piston skirt across the piston pin, as
illustrated.
Piston diameter
450 SX-F / 450 SXS-F
size I: 96.960 - 96.970 mm
size II: 96.971 - 96.980 mm
– The piston mounting clearance is the difference between the
smallest cylinder diameter and the piston diameter.
Piston mounting clearance
size I: 0.030 - 0.052 mm
size II: 0.032 - 0.054 mm
Wear limit: 0.070 mm
If the piston is to be remounted:
– Inspect the parts for damage or wear.
– Replace any damaged or worn parts.
– Piston ring grooves: the piston rings must move freely in the groove.
– Measure the piston end gap.
– Mark the installed position of the oil scraper ring.
Mount the compression ring with the "TOP" mark facing up.
– Replace piston pins that are badly discolored or have visible running
marks. Place the piston pin in the conrod and check for clearance.
– Mount the piston pin retainer on the timing chain shaft side.
505 SX-F
size I: 100.000 - 100.012 mm
size II: 100.012 - 100.025 mm
is marked on the cylinder collar, the piston
505 SX-F
size I: 99.960 - 99.970 mm
size II: 99.971 - 99.980 mm