KTM 250 EXC RACING Owner's Manual page 123

x
y
2
Cylinder – Nikasil coating
Nikasil is the brand name for a cylinder coating process, developed by
the piston manufacturer Mahle. The name is derived from the two
materials used in this process - a nickel layer into which the particularly
hard silicon carbide is embedded. The main advantages of the Nikasil
coating are excellent heat dissipation and thus better power output, low
wear and low weight of the cylinder. The worn coating can be
regenerated at low cost provided that the running surface of cylinder is
flawless.
Measuring piston and cylinder, determining the piston fitting clearance
1
– In order to determine the wear of the cylinder, measure the cylinder
center of the running area with a micrometer.
– Measure the diameter of the x-axis and the y-axis in order to check
for oval wear, if any.
Cylinder diameter 250 EXC
Cylinder diameter 400/450 EXC/MXC size I: 89.000 - 89.012 mm
Cylinder diameter 450 SX/SMR/SXS,520 SX/525
Cylinder diameter 540 SXS/610 CRATE 100.000 - 100.012 mm
NOTE: The size of the cylinder 1 is marked on the cylinder, the size of
the piston is marked at the top of the piston 2.
– The piston is measured on the piston skirt across to the piston pin as
shown in the illustration.
Diameter of piston 250
Diameter of piston 400
Diameter of piston 450 EXC/MXC
Diameter of piston 520
Diameter of piston 450 SX/SMR/SXS size I: 94.932 - 94.960 mm
Diameter of piston 525
Diameter of piston 540 SXS/610 CRATE size I: 99.940 - 99.948 mm
– The cylinder diameter minus the piston diameter yields the piston
assembly clearance.
Piston assembly clearance 250
Piston assembly clearance 400
Piston assembly clearance 450 EXC/MXC size I: 0,054 - 0,096 mm
Piston assembly clearance 520
Piston assembly clearance 450 SX/SMR/SXS Größe I : 0,040 - 0,080 mm
Piston assembly clearance 525
Piston assembly clearance 540/610 0,060 - 0,090 mm
5-8E
size I: 75.000 - 75.012 mm
size II: 75.013 - 75.025 mm
size II: 89.013 - 89.025 mm
size I: 95.000 - 95.012 mm
size II: 95.013 - 95.025 mm
size I: 74.950 - 74.980 mm
size II: 74.961 - 74.990 mm
size I: 88.920 - 88.950 mm
size II: 88.931 - 88.960 mm
size I: 88.916 - 88.946 mm
size II: 88.926 - 88.956 mm
size I: 94.942 - 94.950 mm
size II: 94.951 - 94.958 mm
size II: 94.940 - 94.968 mm
size I: 94.922 - 94.950 mm
size II: 94.951 - 94.978 mm
size II: 99.950 - 99.958 mm
size I: 0,030 - 0,052 mm
size II: 0,032 - 0,055 mm
wear limit: 0,12 mm
size I: 0,060 - 0,082 mm
size II: 0,062 - 0,085 mm
wear limit: 0,12 mm
size II: 0,056 - 0,099 mm
wear limit: 0,12 mm
size I : 0,050 - 0,070 mm
size II : 0,054 - 0,075 mm
wear limit: 0,12 mm
size II : 0,044 - 0,085 mm
wear limit: 0,12 mm
size I : 0,050 - 0,090 mm
size II : 0,034 - 0,075 mm
wear limit: 0,12 mm
wear limit: 0,10 mm