What you are probably hearing is the front sprocket shaft. If you put your bike on the back stand, put it in gear, engine off and roll the tire back and forth with your hand, you will hear it.You hear it on the bike more in first due to the torque coming on and off when you let off the throttle. For the heck of it, check your countershaft nut and make sure its tight. I have seen 2 of them come loose, both on new bikes with low miles.