Re: Motor break in period
I would bet that he over did it. Of course I don't know, but if you do it exactly as motoman states, and CHANGE THE OIL very early on (20 to 50 miles) it should never give you a problem. You have to get the metal shavings out of the oil so they can't contaminate the rest of the system. during the break in you can't change the oil too often or too soon. If it was a bearing failure, the hard run would not have had an effect on whether the engine failed or not. The problem with mass produced engines is that every assembly is rarely quality checked. they do it in cycles- every 50th or 200th engine. this can allow for one or two engines that are barely outside the tolerances to slip through. Think about this... Every component of your bike has a tolerance. what happens if the crankshaft journal is at the largest the tolerance allows, at the same time, one of the bearings is at the thickest the tolerance allows? it causes the clearances to shrink. when these clearances shrink, less oil is allowed into the passage. On a four cycle engine, the moving parts should not touch the bearing. What really happens is the oil pressure causes the oil to surround and push against the journal. When the engine is running, the journal actually rides on the oil not the bearing. this is why when you build an engine you have to prime the oil pump to get oil in all the bearings so they don't burn on the initial start up. When less oil is allowed into the passage, and the parts expand while running, you can actually have these parts touch. This kind of failure would show it's face on any engine within just a few hundred miles usually.
when you do the motoman method. You still have to vary the RPM. you can't just go do a top end run and expect the break in to work. Having built quite a few engines myself, I know for a fact that honing tools have gotten quite a bit finer over the past couple decades and the need for long break in periods is not needed any longer. Ask any NASCAR team how long they break their engines in? I bet it's just a few laps on a short track, or a few runs on a dyno. they don't have time to break an engine in over several hundred miles. and the pressures that the moving parts on those engines suffer is way harsher than that of our short stroke engines.