I read the following in the September 2004 issue of Sport Rider and wanted to pass it along. It's from the 'Ask the Geek' section and sounds like the most reasonable break-in method.
Q. I'm going to buy a new ZX-10R and I was wondering about break-in. Kawasaki says break it in easy, very easy. On a Web site I found it says break it in hard, and that the first 20 miles are the most important. Is this true? The site says the harder you ride any bike at first to break it in the more power it will have when it's fully broken in. Is the Web site legit? I will appreciate any insight.
A. While we generally consider the manufacturer's break-in recommendations to be on the very safe side, trying to break-in your new bike in the first 20 miles is not a good idea. There are two aspects to break-in that need to be considered, and they are at odds with each other. One is that to properly seal the rings with the cylinder walls, sufficient load must be used to keep the rings in good contact with the cylinder -- otherwise the walls will glaze and the engine will have less compression than it should. In contrast, a light load is necessary so that the various bearings and other internals can properly mate -- putting too much load on a brand new tight tolerance bearing will score the surface if there are imperfections that would otherwise be removed by a light break-in.
We've seen many bikes that make more and more horsepower as the miles add up, a good indication that the break-in process takes place over an extended period of time. We recommend following the manufacturer's method, but including the occasional medium load run to higher revs to ward off cylinder glazing. Be certain to finish off the process with runs to redline under load, as that will ensure the final seating of the rings.