Please help. I have a 07 yz450f. It was making a noise I haven't heard before when trying to start it. Randomly (maybe 6 out of 10 times) I kickstart it, I could hear something moving/spinning/rotating as soon as I finished my kickstart stroke with my foot. I took the valve cover off and watched the cam and the noise is the cam is oscillating or bouncing back and forth fast for maybe a second or two as soon as I get done kickstarting it. The timing chain tensioner is fine, the timing chain seems to be fine, nothing appears to be loose or have slack in it either. I talked to a mechanic at a yamaha dealer and he told me depending on where the piston/crank and everything is at the end of the kickstart stroke that if its in a decompression stroke (no back pressure on the piston) the crank could oscillate back and forth briefly before finding its place and stopping. However I find this hard to believe. It seems like there would be or should be too much friction in the system especially with the rings in the cylinder that it wouldn't allow it to oscillate back and forth briefly. Has anyone heard of this or have any advice???? I could start the bike and it ran fine but seemed loud and seemed like it made a little different noise when I revved it up. I know they run loud just not sure how loud is normal.