O.K. - '06 xr650r, uncorked with Edelbrock, 17e needle (I believe), 12 clicks from rich. Bike starts easy, runs great, plug is nice tan color. Usually ride around 2500' elevation (California High Desert). Under load - especially in 4th and 5th gear I'm getting that "marbles in a can noise". I don't think it's pre ignition, but it sure sounds like it. I am assuming it's the counterbalance gears but not sure. Any ideas?