ditch the big bore kit, it will hurt more then help, the transfer ports get cut way down with the big bore, the transfers are the main power maker. port the stock cylinders, cpi pipes, and bigger carbs, or a 350 cub, cpis and bigger carbs. cpi pipes come on alittle sooner in the mid range but will not rev as high as the shearers. me personaly I love my shearers and would not trade them for anything. oh and alot of the 1/4 mile bikes on planet sand run 18/38ish gearing in the 1/4 mile so I would not say it has not been done. most of them are goin mid 90's at the big end.