No need to change the mixture for breakin....Fire it up, make sure nothing is leaking (coolant, gear oil). Let it run until the coolant is barely warm. Kill it, go drink a 6 pack. Repeat this process a couple of times before riding it. Check bolt/hose clamps. When you do ride it, don't go WOT for the first tank. Also, don't let it idle for long periods. After that first tank, ride it like you stole it. Be sure to get in a couple of plug chops to double check your jetting. Have fun.