after warming up, my honda 09 foreman makes a rattling noise at a certain rpm in each gear. at 5mph in 1st gear, at 9 mph in 2nd, at 13mph in 3rd, and 18 in 4th. 1 mph faster or slower and its gone. but it's driving me crazy. will also do it in neutral as you increase the throttle and pass thru that specific rpm. honda mechanic thought it was in the frame - retorqued motor mount, removed and replaced fenders, heatshield, etc. i think its internal as it only does it after warming up. only 180 miles and done it since day 1. help!