Front sprocket

its easy, loosen the bottom bolts and pull the bottom part of the carrier and see if you can pull it back,might be diff on mine because i have a +3 but i think they are the same. you don't want to pull it all the way back because over time the chain will stretch, you want a little leeway, so you are better off pulling a link out, and its 2 fingers, how you measure the tightness of chain.
 
wut has to be grinded in order to fit the 15t sprocket? the flywheel plastic cover thing?



also where would i order the sprocket from