i break in the 2 strok slightly different than a 4, my yfz450, i warmed it up fully, and literly rode how i normally would right from the start, my stupid ass manual says to break it in and take it easy for 20 hours, no joke. this will not cause a good seal for the rings, blow by will occur, and this is not good for 4 strokes, contaminated oil and less power etc. my bike runs extremely well, in short dont listen to the manual. they want your bike to break down earlier. funny how lots of people say take it easy while you break it in, thats a joke, i know this isnt a perfect comparison, but on chainsaws trimmers, etc etc, you mix the oil, start it up and start cutting some dam trees down full throttle right off the bat, guess what, those chainsaws last forever!!!! even with hard breakins, ive worked on them i know. the best thing you can do is warm up the bike fully before every ride and mix the oil at around 32:1 and have it tuned right.