unscrew the nut under the sink and then you can turn the lever counter clockwise, sometimes there is plumbers putty that makes it hard to unscrew the lever without taking the nut under the sink off, watch this link
https://www.youtube.com/watch?v=zc7Q5666yoU
Answer from user111874 on Stack ExchangeVideos
Need help to take out Kohler faucet cartridge.
How to replace valve cartridge on Kohler DevonshireWidespread bathroom sink faucet - Home Improvement Stack Exchange
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How to remove Kohler Memoirs faucet handle (and replace cartridge)?
I can’t get this cold water faucet cartridge loose, it feels completely stuck. Tried with a ratchet, extra person holding the faucet in place, used CLR, nothing I tried works. What am I doing wrong? I don’t see visible rust so I’m surprised it’s so stuck. Please advise. Thanks!
unscrew the nut under the sink and then you can turn the lever counter clockwise, sometimes there is plumbers putty that makes it hard to unscrew the lever without taking the nut under the sink off, watch this link
https://www.youtube.com/watch?v=zc7Q5666yoU
Give Kohler a call. All their products carry a lifetime warranty or at least they used to, They can explain the procedure you are looking for and send you the repair parts free to you.