Hey I recently purchased a piston for a 1985 Cr250r dirtbike. When I bought the piston the guy I bought the dirtbike from said that the dirtbike was a 1989 so thats the piston I ordered. When the piston came he said oh thats right the bike is an 85' and between the year of 1985 and 1989 they changed the dirtbike from 246cc to 249cc Im going to get the cylinder bored out, but how much should it cost ?