I like the break it in hard way. I think it breaks the myth about easy break ins, and you get a better running engine because of reduced blow by (exhaust gas blowing by the piston ring druing the power stroke). I just warm it up on the stand for 5 min, while reving it and rough tuning the low speed jet (knowing the high is rich). I just let it cool once, and you probably don't have to. I still have some of the myth in me too I suspect. Then I run em--but I work up from 1/2 throttle -- check the plug, then run a little higher RPM and check the plug. When I get to full throttle and plug checking and have it running crisp with a light brown color--it is ready to race. The whole idea is to seat the ring as fast as possible to the cylinder wall. This is suppose to reduce tarnish build up that is caused, and causes blow by. When your in the good power, you build up cylinder pressure. The pressure pushes the ring from behind up against the cylinder wall to seat it in faster, before tarnish can build up (and if the cylinder was honed--before the honeing gets a bit smooth). When I see a engine that was broke in extreemly easy, or somebody running 50:1 in a gas/oil mix on a 18,000RPM ringed engine, I allways see the dark marks on the side of the piston indicating blow by. Break it in fast, and the piston stays clean--meaning no blow by. I have never seen a failed Zen or Zen type engine because of going wide open right out of the box and not breaking it in. All I have seen are other failures that customers thought happened because of not breaking the top end in the way the myth says. They failed for some other reason--usually running lean and seizing.