well, where do we start! your bike is a carburettor model kawa so i'd start by assuming you've got dirty carbs as often a fault with carburation will only show up when load is apllied to the engine yet the engine will rev freely whilst in neutral with no load. has your bike been laying up for a while or has anything happened recently that could have caused this problem?? does your bike live outside in the rain or is it garaged?? please give us a bit more info mate. :)