i still prefer ur avatar ....
Bore = Diameter .. width of a piston .
Stroke = how much distance the piston travel from TDC to BDC
4B10 -> Bore = 86mm Stroke = 77.4mm
4B11 -> Bore = 86mm Stroke = 86 mm
4B12 -> Bore = 88mm Stroke = 97 mm
Calculation pretty simple ..
PI x ((Bore / 2 )^2)/1000 x (stroke) x (number of piston)
PI is constant = 3.142
take 4B10 as example ..
(3.142) x ((86/2)^2)/1000 x (77.4) x (4)
(3.142) x ((43)^2)/1000 x (77.4) x (4)
(3.142) x (1.849) x (309.6)
= 1798 cc ...
4B11 as follow ....
(3.142) x ((86/2)^2)/1000 x (86) x (4)
(3.142) x ((43)^2)/1000 x (86) x (4)
(3.142) x (1.849) x (344)
= 1998cc ...
TADA!
Now .... story can continue ..
increase either BORE SIZE or STORKE will increase the capacity ..
due to the reason 4B10 / 4B11 same block but diff stroke kit ..
that is why 4B10 can stoke it up to 4B11 spec!
Longer stroke .. engine slower response ..
KOPY KOPY KOPY
LOnger stroke but slower response....