Specification Desc./Quantity
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).
Slot packing system
Shimming system for limiting the compression ratio Rc = 10.5 : 1
DISTANCE "A" IS A PROJECTION OR RECESS VALUE OF THE PISTON TOP FROM THE CYL-
INDER PLANE.
DISTANCE "A" ALLOWS THE THICKNESS OF THE GASKET TO BE DETERMINED THAT HAS TO
BE FITTED TO THE CYLINDER HEAD IN ORDER TO RESTORE THE COMPRESSION RATIO. THE
BASE GASKET MUST BE THICKER, THE MORE THE PLANE FORMED BY THE PISTON TOP
PROTRUDES FROM THE PLANE FORMED BY THE CYLINDER HEAD. ON THE OTHER HAND,
THE MORE THE PISTON TOP IS RECESSED INTO THE CYLINDER TOP PLANE, THE SMALLER
THE GASKET THICKNESS.
BASE GASKET THICKNESS
Name
Measure A Thickness
«A» MEASURE TAKEN - 0.185 - - 0.10 0.4 ± 0.05
«A» MEASURE TAKEN - 0.10 - + 0.10 0.6 ± 0.05
«A» MEASURE TAKEN + 0.10 ÷ + 0.185 0.8 ± 0.05
N.B.
VALUES INDICATED WITH «-» REFER TO PISTON CROWN RECESSES WITH RESPECT TO THE
CYLINDER PLANE.
Characteristics X9 Evolution 500
CHAR - 18
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