Gilera Nexus 500, Workshop Manual, Page: 16 / 406

Specification Desc./Quantity
B: 43 mm
CATEGORIES OF COUPLING
Name Initials Cylinder Piston Play on fitting
Cylinder Piston A 91.990 - 91.997 91.954 - 91.961 0.029 - 0.043
Cylinder Piston B 91.997 - 92.004 91.961 - 91.968 0.029 - 0.043
Cylinder Piston C 92.004 - 92.011 91.968 - 91.975 0.029 - 0.043
Cylinder Piston D 92.011 - 92.018 91.975 - 91.982 0.029 - 0.043
N.B.
THE PISTON MUST BE INSTALLED WITH THE ARROW FACING TOWARDS THE EXHAUST SIDE,
THE PISTON RINGS MUST BE INSTALLED WITH THE WORD «TOP» OR THE STAMPED MARK
FACING UPWARDS.
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.
Characteristics
Nexus 500
CHAR - 10