I have a 2002 ninja 500 with a vance and hines exhaust. Thats about it. I am going on the highway and this just happened to me.. Anyways im about 1/4 of the throttle in 6th gear and when i try to accelerate more the machine bogges down and doesn't speed up. But if i let off the throttle it goes fine but only at 1/4 of throttle. I have premuim gas in the machine. Just did and oil change? What could be the problem. Could the petcock be at the wrong position i have it vertical down at ON but would it matter if its a little in the off position? Also seemed to do it while i was cruising around 35 and i try to accelerate it bogges down. Almost like its out of gas. But i still have a half a tank.