The basic formula for Engine capacity is:
CC=( Pi x D²xS)/4000
Where:
PI = 3.1416
D = Bore diameter in mm
S = Stroke in mm
Please note it is the stroke of a crank not the conrod length which is used for calculating CC
Std lamy stroke 58mm
Typical over stroke 60mm 62mm 64mm
Short stroke 54mm
60mm can be installed with no mods to crankcase
62-64mm need a groove machined into the crankcase to allow for conrod to rotate without catching also may be some welding.
typical Lambretta CC's and how to get them
stroke 54mm Bore 60mm CC=152.68
stroke 58mm Bore 52mm CC=123.18.......Std 125cc
stroke 58mm Bore 57mm CC=148.00.......Std 150cc
stroke 58mm Bore 62mm CC=175.11
stroke 58mm Bore 64mm CC=186.59.......for 190cc
stroke 58mm Bore 66mm CC=198.43.......Std 200cc
stroke 58mm Bore 67mm CC=204.49.......for 205cc
stroke 58mm Bore 70mm CC=223.21.......for 225cc
stroke 58mm Bore 71mm CC=229.63
stroke 58mm Bore 72mm CC=236.15
stroke 60mm Bore 70mm CC=230.91........for 230cc
stroke 60mm Bore 71mm CC=237.55........for 240cc
stroke 60mm Bore 72mm CC=244.29........AF 250cc I call it 245cc ?
stroke 62mm Bore 70mm CC=238.60
stroke 62mm Bore 71mm CC=245.47
stroke 62mm Bore 72mm CC=253.43........A true 250 thumper
Well stroked
Stroke 64mm Bore 72mm CC=260.58.......A monster
Hope this gives a simple basic insight to CC
Smiffy (RinB)
