remove the only 2 mount bolts that hold the starter on and the nut holding the main wire then pull the starter straight out, though usually you'll have to pry it out.
Apply WD-40 or any type of penetrating spray and let it work for at least 20 minutes. If the bolt is strong you can simply place a properly sized socket wrench over the bolt and use a box-end wrench...
I have a 2001 250 quad runner. I just finished changing my oil. You must jack up the rear end of the ATV and put jack stands underneath to supportit. Remove the back right tire. The oil drain plug is...