Aftermarket Pistons

It all depends on the size that you had before. If your cylinder walls are good then stick with the same size. Just get a hold of a micrometre, you could buy a cheap one but what i'd do is go to your local dealer and they should be able to measure it for you at no cost. Then call wiseco give them the measurements and your on your way

There is more to a piston that its diameter. The piston has to be made for your particular application.

Ring placement, pin size, port location...all (and more) are critical and must be addressed.

Just 'cuz Wiseco doesn't list one doesn't mean they don't have one. Call, write or email 'em and ask for the piston for your particular bike.

Of course if it's a known fact by other owners of your kdx that an 'X' type piston indeed fits a 'Y' type bike, fine.

I have no idea if an '86 fits an '83.