I've actually posted about this issue before. My NSX experience started 4 years ago with a '91 fitted with an RPS clutch. The pedal pressure was unbelievably hard. I was told it was just the nature of that clutch. After about 10K miles, I put on an OEM. The pedal feel was very light, like it's supposed to be, but after a couple of weeks, got much heavier than my friends NSX's with other OEM clutches. So I changed the clutch master and slave. Initially it felt great, but after about a week it was stiff again. I was then told that the throwout bearing probably wasn't greased correctly, so I had the clutch fork and throwout bearing lubed, which made it better...for about a week, then back to being stiff. So I just had a Science of Speed Sport clutch installed and specifically told them to make sure everything was well lubed with the high temp Honda Urea grease. As usual, I drove away with barely any pressure needed to depress the clutch. Now after a few weeks, it's stiffened up much more than it should be. The heavy clutch pedal causes me to keep it depressed more than I should, which is shortening the life of each of these clutches. What's the deal? All I can think is that the fluid is not right. Any advice would be appreciated.
