OK i have a 03 prairie 650 (witch i hope soon i will be up gradeing to something with decent power!!) and ive been hearing a thump and clicks while ridding it, and today it got real bad. even when it is off and i shake it side to side it does it and i can even feel it in the quad. what is wrong with it and is it hard to fix???

 

If it is coming from the back it sounds like swingarm bearings go to nyroc's site i believe there is a how to on there

 

Also check your front motor mounts, they are often loose and cause a similar noise.