I replaced my K-240's foam nets and the headphone is like new right now. I also changed pads, feels great.
It's been almost 10 years since i had my K-240 and i started hearing a buzz noise from left. I thought it's broken somehow but turned out that foam net got into headphone membrane. So, i cleared it and problem solved. Then, i ordered new set of foam net and pads. I am so happy now, enjoying my K-240 again.