i have a mostly stock 07 yfz 450 and im about to start doing some work on it but what is the stock bore/ stroke for this year? im looking to get a 13.1 piston along with alot of other things but i want to make sure i get the right one. i will be ordering my parts tuesday. i was also wondering, i was looking at this stroker kit that comes with the 13.1 piston is there any mods that would have to done in order to instal this, like any machining? how hard is it to instal a stroker kit? any one have some sort of guidlines, videos , instructions for me?