Not ideal to use WD40 on calipers it doesnt do the seals any favours. sounds like they need a proper strip. pistons need removing, remove the seals, clean and scrape away all the corrosion in the recess, and if the seals are in good order refit, likewise for the pistons. any corrosion then replace,
SOunds like it will be less hassle to do a part ex with graeme france for a set of refurbed ones.

might give that a try, how would i be able to contact the guy and how much would it cost?

also does he refurb other calipers? my fzr250's calipers were pretty gash when i bought the bike.