Here's the problem. I just bought a 2006 DRZ 400 SM with 4300 miles. The bike runs flawlessly, but just off idle in all gears, I'm hearing a rattle or knocking sound. I hear it until the rpms get high, but I don't know if it goes away, or if the wind and other engine noise drowns it out. I've had two other DRZs, and I don't remember them having this noise. I'm no mechanic, but to me it sounds a lot like what I call piston slap. The kind of sound you get if you lug the engine in higher gears, and now I focus on the noise as soon as I start riding. Also, I don't hear it with the bike in neutral revving it in the driveway. I know it's hard to judge without hearing it yourself, but have any of you had this similar issue? I don't really want to take the bike to local Suzuki dealer because I haven't had very good experiences with their service dept. The guy I bought the bike from is a friend, and has agreed to make things right if there is a major problem. Help! I don't want to dislike this bike because of a simple problem.