Kurzweil requires the wiper of the pot to be connected to the tip, the top of the pot connected to the ring and the bottom of the pot connected to the sleeve. Roland wires their pedals this way. Yamaha pedals flip the tip and sleeve connections. For a Yamaha CC pedal to work smoothly with a Kurzweil you need to reverse the tip/sleeve either by building an adapter yourself or purchasing one of these:

http://music.ashbysolutions.com/misc.htm

I recommend a yamaha FC7 with the above adapter for the Kurzweil. Nice long, smooth sweep and reasonably priced. I use one with the PC3 for controlling KB3 expression. It works great.

mine works fine wired like this:

Thanks to both for your answers, I thik wirings of the pictures are good.
Today I made an adapter cable from FC7 Yamaha pedal to Kurzweil PC3K

In the cable swaps TIP and RING connections so the WIPER signal of the FC7 potentiometer shifts from RING to TIP of the stereo plug and TOP signal of the FC7 potentiometer shifts from TIP to RING of the stereo plug.
With this adapter cable FC7 works but the first 50% of its run has volume = 0 or very low volume, then the second 50% of its run has a good control. This is because Kurzweil requires 10K ohm potentiometer and FC7 has 50K ohm potentiometer.

Now I can use FC7 pedal with Korg M50 and FC7 + adapter cable with PC3K6.

It would be so good if Japanese, Korean and USA manufacturers could set a standard (wirings, ohm resistance, log or linear scale...)

With this adapter cable FC7 works but the first 50% of its run has volume = 0 or very low volume, then the second 50% of its run has a good control.

i use the fc7 with the pc3 and i get a smooth sweep from beginning to end, as validated through midiscope. Something seems amiss; try reversing the tip and the sleeve and see if you get a smooth run of volume from beginning to end. Your keyboard is the same as mine so the only logical explanation is that the tip/sleeve are backwards. Since you said you 'made an adapter' simply remove the adapter and try it. Keep in mind that the pc3 'reads' the pedal and polarity on powerup. So first connect the pedal with the adapter and then powerup the Pc3. If the pedal still doesn't work smoothly, remove the adapter you've built, power off the PC3, then plug the fc7 into the pc3, then power on the pc3, then try it again. One or the other should provide a long, smooth sweep from beginning to end. The only other logical explanation is that the adapter is wired incorrectly and is not actually reversing the tip/sleeve. Recheck your wiring and be sure your adapter actually is reversing the tip/sleeve. If it isn't right then, on or off, the polarity will be the same. I made my own adapter and got it wrong the 1st time. I reversed the tip/sleeve on one end of my plug (even though i thought it was correct) and then it started responding correctly.