Beta RR 4T - 525 - Page 65

36
Manuale di Officina RR 4T - 250 - 400 - 450 - 525
Cylinder - Nikasil lining
Nikasil is the trademark of a cylinder lining procedure developed
by the piston manufacturer Mahle. The name is derived from the
two materials used in the procedure – nickel containing silicon
carbide to make a particularly hard substance. The principal ad-
vantages of Nikasil are excellent heat dissipation, making for an
increased power supply, and reduced cylinder weight and wear.
When worn down, the lining can be restored (replaced) at a low
cost providing the cylinder sliding surface is not damaged.
x
y
Measuring the piston and the cylinder - Determining the
piston fit
– To determine how worn a cylinder is, measure it at the centre
of the sliding surface with a comparator.
– Measure the diameter along axes X and Y to determine
whether any ovalization is present.
Cylinder diameter 250 size I cylinder: 75,000 - 75,012 mm
size II cylinder: 75,013 - 75,025 mm
Cylinder diameter 400 - 450 size I cylinder: 89,000 - 89,012 mm
size II cylinder: 89,013 - 89,025 mm
Cylinder diameter 525 size I cylinder: 95,000 - 95,012 mm
size II cylinder: 95,013 - 95,025 mm
Cylinder size 1 is stamped on the cylinder side in front of
the chain tunnel; piston size 2 is stamped on the piston
top.
- The piston is measured on the skirt transversally to the piston
pin as shown in the figure.
Piston diameter 250 size I piston: 74,960 - 74,970 mm
size II piston: 74,971 - 74,980 mm
Piston diameter 400 size I piston: 88,930 - 88,940 mm
size II pistonI: 88,941 - 88,950 mm
Piston diameter 450 size I piston: 88,916 - 88,946 mm
size II pistonI: 88,926 - 88,956 mm
Piston diameter 525 size I piston: 94,942 - 94,950 mm
size II pistonI: 94,951 - 94,958 mm
- The piston fit is obtained by subtracting the piston diameter
from the minimum cylinder diameter.
Piston fit 250 size I pistonI: 0,030 - 0,052 mm
size I piston: 0,032 - 0,055 mm
wear limit: 0,12 mm
Piston fit 400 size I pistonI: 0,060 - 0,082 mm
size I pistonI: 0,062 - 0,085 mm
wear limit: 0,12 mm
Piston fit 450 size I piston: 0,054 - 0,096 mm
size I pistonI: 0,056 - 0,099 mm
wear limit: 0,12 mm
Piston fit 525 size I pistonI: 0,050 - 0,070 mm
size I pistonI: 0,054 - 0,075 mm
wear limit: 0,12 mm
1
2