KB -
New engine or complete rebuild:
1 - Run first until warm to the touch, on the cylinders. Moderate to fast idle. I'm usually adjusting the carburetor low speed setting.
2 - Let sit for 10 or 15 minutes, and snug all head bolts and cylinder base bolts (no thru bolts on any of the machines I deal with).
3 - Let sit until cool down to ambient temp..
4 - Run until warm to the touch, as in first step.
5 - Repeat 2nd step, except snug head bolts, only. Feeling for creep, and not pulling hard.
6 - Cool down to ambient temp..
7 - Repeat steps 4,5 & 6, until no creep felt in head bolts.
8 - Hit the back roads with no traffic, accelerating easy, never lugging the engine in any gear. Time the ride to coicide with a cool-down stop, every 15 or so minutes. Cool-down means I don't burn my hand, when I'm checking the temperature. Back side of the hand and fingers, only. Nothing like holding on to the handlebars with a blister. I try to make these first trips in the cool of the evening. Winter is my favorite break-in season.
9 - Repeat step 8 for a couple of weeks, never getting over 45 - 50 mph in high gear, on level ground. Never run in high, for extended periods, when pulling a grade. RPM's are not the issue, so much as the load.
10 - Change the oil, but not the filter. It ain't through working, yet. And, it certainly hasn't gone bad. Don't pay any attention to the miles.
11 - Hit the open road, staying under 60 mph. Ride at mostly varying speeds of 45 to 55 mph. Mostly level roads or easy grades, if possible. Cool-down periods every 30 minutes or so.
12 - Repeat step 11 for a couple of weeks.
13 - Change the oil and filter (it's still working, but just change it) at 500 or so miles, or end of 2 weeks. Whatever comes first.
14 - Repeat steps 11, 12, & 13, change oil and filter at 500 mile intervals up to 2500 miles.
15 - Take it on whatever trips, and whatever road speeds you feel like.
I would have ended the break-in at 1500 or so miles, with dino oil. So, there is only a short extention in miles. Time seems to be the greatest extention.
The tranmission lube gets changed with the second oil change, and the last, before hitting the road for a trip. But, the grade stays the same for the first riding season. I make the jump in grade on the next season. I used to flush with kerosene, but now use syn ATF.
This applies to all vintage models that I build. We're talking cast iron, and hot, for cylinders, and some flatheads.
Jack