Need Some Help....

I just got a new renthal 13t sprocket for my 06 yfz to replace the stock 14t. When i put it on and got i all tightened up, i went to tighten the chain so i could go riding, but for some reason, when i push the quad back to tighten it, it doesn't catch(or whatever you wanna call it) and it wont tighten and the hub stops the quad..... :angryfire: I'm totally stumped. I need some help really fast so i can get riding again. Thanks.