Piston rings
* Fit rings «2» and «3» with the word «TOP» facing upwards.
** Position the openings in the rings as shown here.
*** Value «A» of sealing ring inside the cylinder
**** Ring opening
SEALING RINGS
Name
Initials Cylinder Piston Play on fitting
1st Compression ring A 0.15 ÷ 0.35 0.5 </>
Middle piston ring A 0.25 ÷ 0.50 0.65 </>
Oil scraper ring A 0.25 ÷ 0.50 0.65 </>
Crankcase - crankshaft - connecting rod
Crankcase / countershaft coupling
Besides considering it should match the crankshaft, the crankcase is chosen according to the centre
to centre distance between the seat of the crankshaft and that of the contra-rotating shaft.
Both the centre to centre distance and the pair of gears driving the contra-rotating shaft are divided into
two types (A and B) to be matched (A with A and B with B).
This selection is useful to keep the difference between the working distance of the gears and their
distance without clearance at a given value in order to avoid abnormal noise.
TYPE A
Specification
Desc./Quantity
Centre to centre distance of the gears without clearance 76.937 ÷ 76.867
Centre to centre distance on the crankcase 77.022 ÷ 76.992
TYPE B
Specification
Desc./Quantity
Centre to centre distance of the gears without clearance 76.907 ÷ 76.837
Centre to centre distance on the crankcase 76.992 ÷ 76.962
The gears with centre to centre distance without clearance between 76.867 and 76.907 are considered
universal and can be fitted to either crankcase type.
Either the pair of gears or the crankcase is identified with the letter referring to the type (on the crank-
case, this mark is found at the cylinder mouth, flywheel side).
Characteristics Nexus 500 euro 3
CHAR - 14
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