Well I have always have had a little chain slap on my WR450, and could never really get rid of it. Well, I was on a fire road last Sunday and really listened to the noise. I put my head down near the engine, as I was never really sure if it was detonation or chain slap. Well, the sound near the engine(it is hard to hold your head low going 50MPH) was definatly detonation. It sounds very similar to chain slap. Well, it turns out, my first 150 break in miles was full of detonation. Probably not a big deal, but I'm sure glad that I found it early. A couple clicks on the needle fixed the problem. I suggest that everybody that has the "chain slap" noise first adjust the chain to spec., and pay attention to the sounds your bike makes. Detonation is hard on your crank, piston and valves. Just FYI. Yoda'