In
post #93 ... I said I believe the reason the gap decreases over time is because the soft aluminum head material is being compressed incessantly by the hardened valve seat every time the valve springs shut. I stand by that belief after reading about ST-owners who performed follow-on gap checks found no further change. Sure, the valves and seats may wear a bit, but usually a minuscule amount if the hardened steel is of good quality. So how does Mother Honda install the valve seats? Do they push them into the heads until a pre-set amount of pressure is built up? Or do they merely press them in to a constant depth dimension? Regardless, I agree that they should be checked at least once ... probably around 40k or 50k miles. After that, fuhgeddaboutit.