I have a rattle when accelerating (just normal acceleration, not hard) with a cold engine at 2700 rpm and above. Once the engine is completely warmed up, the rattle completely goes away. Bike runs very strong. Motor is stock except for a SE air intake and a V&H fuelpak. I thought it was pinging, but careful listening makes me believe it is mechanical. I will be trying to get it to the dealer this week for warranty. All fluids are up to spec. It is an '08 Ultra.