"In my K2500 I would like to be able to take a sample and create a keymap with different decay lengths. What is the best way to accomplish this?"

You can edit the Decay Rate for an individual sample on the MISC page of the sample editor. So you could edit that sample and save it with different Decay amounts as several different samples.

When you save to a different number, the Kurzweil will ask if you want to save the sample data as well. If you answer yes, it will make a copy of the sample data, thereby using up more sample RAM.

If you answer no, then it will save only a sample header, consisting of the Start, Alt, Loop, and End points, plus the values of the parameters on the MISC page. This obviously saves sample RAM, but the disadvantage of this method is that if you make any changes to the original sample that actually changes the sample data itself (by using any of the DSP functions) it will affect all the sample headers that access that same data.