I have a 1999 honda foreman 400 and it ran like a champ when i got it nothing sounded broken or unusual at all sounded perfect but my front differential mounts broke so i differential was only help in by the axles and the shape of the frame. It wasnt enough that it would fall out it was rideable and i ordered a new diff but tonight while riding down the road it started to whine like the engine sounded whiny so i stopped on the side of the road to see if anything was wrong and it started to go away but got worse at higher rpms. The whining stopped and a ticking noise started and got worse at higher rpms. Everything works great on the bike and was owned by an old guy and was kept in his barn most of the time so im wondering what could be wrong before anything further breaks. Sorry for the really long explanation just like to add detail.