Just some thoughts,
Load is more important than revs. When loaded, the combustion pressure gets forced behind the ring groove and forces the ring out which helps it mate the new ring surface to a freshly honed bore. You have a limited window in which to take advantage of this before you wear that ring in against the new bore/hone properly. Thats why its no good to let it sit there and idle on a fresh build, because all your doing is wasting the opportunity to make a good ring seal by wearing out the cross hatch you put in there in the first place for that very reason. You want to get those surfaces mating under load to get a good seal for a long time.
On a new motor, everything is tight, so you need to keep the revs moderate to start with, but you have to give it load, so get climbing some hills. In doing so, you also need to keep temperature in mind because everything is going to run a lot hotter until its all run in due to increased friction, so after a short run, let it cool down again and repeat. After 20 to 50kms of riding, the piston has already gone up and down thousands of times, so you can imagine what its taken off the liners & ring surface in terms of shavings in such a short time on a fresh hone. You will see this as glitter (a lot of it) in your first oil change. Thats why its real important to change your oil and filter on the first change because the engine is spewing this stuff out. You will find this glitter in the oil, but also when you take your filter out, rip it apart and take a look at what you will find in the bottom of the v-grooves and also in the bottom of your filter housing cup. Get some between your fingers and give it a rub and you will quickly understand whats going on in your motor.
As you start to put on more kms, continue to increase the revs. You will get more shavings, but they will be a lot less in quantity, even with more kms.
As someone said, use cheap crappy mineral oil without friction modifiers for the first 1000 miles at least before going to something better. You want the surfaces to marry (with clean but crappy oil), then once thats done, put something decent in there. After a few several thousand kms, it would be good to pull the pan and clean the screen as well.
Modern engines still are honed in the same manner, but these days they finish it off with a plateu hone which knocks off all the high peaks but allows good oil retention in the lows, making for a motor that requires less & quicker break in than a traditionally honed one. A few hard runs and its all done.
So the short of it is, think load first, then revs, and as it starts to free up after some kms, increase the revs and keep giving it more load at the same time.
The following pics (in this order) are:
(1) Filter ripped apart - have a look at the particles in the v-grooves
(2) same as (1) but reverse/clean side of the filter for comparison
(3) Cup housing.
All this happened in the first 20kms.
This is why I also like this idea
http://forums.sohc4.net/index.php?topic=103432.0&
http://forums.sohc4.net/index.php?topic=137793.0There are different schools of thought on the matter. These are just my thoughts & something thats worked well for me over the years.
