This sleeve exterior diameter is 83.00mm, DON'T NEED MODIFY ANY OTHER PARTS, CAN INSTALL DIRECTLY. Can fit all years GN250 GZ250 TU250 SP250, Before 1989 DR250 LT250... Old GN250 cylinder volume : stroke 61.2MM`bore 72MM =actualdis placement 249cc.
New GN300 cylinder volume : stroke 61.2MM`bore 78MM = actualdis placement 298cc.