smokes

picked up my kz in the fall, changed oil right off. put bout 200 miles on it since then, last weekend i noticed oil was black. bike sat 18 years before i brought it bacxk to life, so i figured the new oil cleaned all the out crap out of the engine. well i changed the oil again, and filter; yesterday i rode it for the 3rd time since i changed the oil. this time when i started it up the bike was blowing blue smoke, i know my kz is old but this is the first; oh and as soon as it was warmed up it stopped. is this normal. thx tim

probably valve guide seals leaking.

You changed the oil, but you didn't mention changing the filter?
Chances are the old oil filter (and possible the oil pump screen) are clogged up with old sludgey oil, and mixing with the new oil creating the black colored oil you're seeing in the oil view window.

Even when you feel that all the oil is drained out, there is always some that remains in oil passages and in the oil pump that will mix with any new oil added. So aside from dropping the oil pan and cleaning/flushing it all out, it just may take a few oil changes to clear it up so the oil at least looks somewhat cleaner.

The blue smoke would lead me to believe that oil is bypassing the oil ring on the piston when cold, and then it's expanding enough to form a seal once it's warmed enough. It could also be a leaky valve seal(s).
A leakdown and compression check should point you towar a possible culprit.