I have an 02' s2k that I've owned for about eight months now and sometimes when I start the car I get a clacking noise. Not on every startup, but maybe one or two out of ten. It sounds like valve clatter but after a couple of seconds it goes away completely and the engine sounds fine. I was told it could be the timing chain tensionor but I thought that made a constant noise all of the time, same for the valves. My car has 70,000 on it and it had 63,000 when I got it and it always done it but I've never had a serious problem. The mechanics at the local honda dealership have never worked on an s2000 before, they told me this, so any work done to this car will be done by me. When I took my car down to the dealership the head salesman said hey, we sold one of those once a few years ago.

 

found this, hope it helps
https://www.s2ki.com/forums/index.php?showt...0&#entry3583234