Brakes are 23 years old everything works, I am replacing the lines, they are not leaking.

Now do I take good working calipers apart and rebuild or leave good working factory seals out and put fresh ones in?

I can argue that leave good one alone or put fresh parts in and risk fubaring it...

I only dealt with one bad caliper on all the cars I have owned and it was leaking.

What do you do?

I would replace the brake fluid with fresh, check the pads and replace them if they need it. I see no reason to replace the piston seals if everything is working though. I suppose if you have reason to suspect that the calipers are full of condensate and gel then you could... but factory seals are undoubtedly better than questionable replacements. If you replace, I would try to find real Kaw parts.

Also, 23 years old? Are you talking about the 2012 listed under your username? 10 years old or 23 years old, if the system holds pressure I would not mess with the seals. Fluid should be replaced every two years.

Also suggest only changing one at a time such as only the rear or only the front :)

My philosophy is if it's working fine leave it alone ! too many other things need immediate attention on a bike ! if the bike is in great shape and needs nothing else and your looking for something to fix regardless.... go take a hike or something leave the bike alone ! LOL:rotflmao:
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Bob......

Remove calipers, remove pads & give the inside of caliper a good clean & degunge. No need to strip caliper if its working good.