The poster regarding Hondas was referring to CRF owners mostly, but the issues with Honda's titanium valves bear much more on quality, process, and material selection than on Ti vs. stainless. Apart from that, the specific info regarding how a specific Honda was originally outfitted is not only an improper subject here, the likelihood of getting good info on the matter is simply going to be much better in that forum than this. The main issue at hand with Ti valves as used in a Yamaha is that titanium itself is not natively hard enough to serve as a valve face. Ti cannot be hardened, either locally or generally, to a point where the wear properties will be adequate for the job without making it brittle. The material does adapt itself very well to extremely hard coatings though, and so various derivatives of titanium nitride are used on the faces. This coating, however can only be applied in a very thin layer. the coating used by Yamaha wears exceptionally well in combination with the seat materials they use, but once it finally wears through, very rapid wear beyond that point occurs, and if ignored, this can lead to a major failure. You have no way of predicting when this point will be reached, it just all of a sudden is. Stainless steel, on the other hand, is much harder than Ti to begin with, and can (depending on the specific alloy) be hardened fairly well without an important loss of strength. But the snag is that not all SS valves are made with hardened faces. Some are coated just like Ti valves, and will suffer from the same sudden acceleration of wear when the coating finally fails. Valve recession proceeds quite a bit more slowly from that point than with Ti, but it happens at a fairly quick pace nevertheless. To the best of my knowledge, Yamaha OEM SS valves are hardened.