Roll pins have to be removed from both drives shafts and moved out of the way,the eccentric shaft can be knocked out enough and the sprocket can be removed. Check out the eccentric bearings plus best to replace the seals. OPT

 

Ok so I got the new sprocket on but I cant get the chain on I tryied to move the front tightener and ive had no luck i loosened the two bolt under the tightener I used a good punch though the sprocket into the tightener and tryied rolling the quad and no luck did I miss a bolt or something?

 

You have a tightener bolt 5/8" at the bottom and a nut on top(down in the recess area) you have to hold to loosen,but DON'T take the nut off!! which take the tightening tension off the eccentric!) If you have the front eccentric moved toward the FRONT as far as possible which loosens it,then loosen the center eccentric 5/8" bolts and TIGHTEN (move the eccentric toward the rear of the atv with a dull punch on the tabs of the eccentric) which actually allows more room to to put the front chain on! When you get the front chain on and the master link, adjust the middle chain FIRST to where you have about 3/8" slack in the middle,then adjust the front chain(if it's a new chain tighten to about 1/8" slack!) After you put a few miles on it,the chain usually stretches. Check that you still have about 3/8" on the center chain,adjust if needed and adjust the front again if necessary to get about the same 3/8" slack in the middle. Any time you adjust the middle eccentric,it affects the tension on the front chain! Also if the eccentrics are hard to turn, use penetrating oil around the eccentrics and just a little heat if necessary. OPT