I've been having a problem with my ATV for a while now, I first noticed it after I put my new belt on so I think it happened when the belt was wearing down and finially went. The problem is when I drive it forward there's a large clunk every 5-10 secs coming either from the rear or center left hand side, it has no power at all and when the bike is turned off and I push it forward in neutral you it will either stop dead or I can hear the clunking noise. I'm taking it in the shop tomorrow but, I'd like to know what's wrong before I take it in.. If anyone has any ideas that would be great.

Thanks