the formula is the bore squared x 3.1416 x stroke. so on a stock lt250 bore is 67 mm so bore squared is 33.5x33.5x3.1416x70=246.7cc

 

Bore divided by 2= A.....AxAx3.14x stroke,divided by 1000=cc's

for example: the stock bore of an Lt 500 is 86mm,so 86 divided by 2 equal's 43mm.

multiply 43 time's itself you'll get 1849,time's that with 3.14,you'll get 5805.86,time's that by the stroke,86 mm,you'll get 499303.96,divide that by 1000 you'll get 499.30396,round it off,and waaalaaa 499cc's.

 

Bore x Bore x .7854 x Stroke