I own an 2005 Shadow Spirit 750. I have read that many riders change sprockets. Can someone explain to me why. Also we ride two up on this bike a lot in steep mountains, and freeways for some kinda long rides I guess. I know the sprocket changes can give quicker starts, and or better gas mileages, depends on what you do. I would like better mileage as long as low gear will pull us up hills. Any suggestions?