These 500s were basically designed in the late forties and were intended for the working man to commute on the road of the 40s and were not categorized at sport bikes. As we called them then, they were duffer bikes made to use the roads of the day and cruise 40-50 mph.
Royal Enfield, England, made some somewhat sportier versions in the late '50s and '60s, but these were not what the Indians were building. They had contracted to build the '55 version and made little attempt at upgrading them over the many years of production as they were originally meant for their police and army. Had Enfield remained in a good business stance in the60s they probably would have produced a unit construction 500 as they already had a 250 and 350 unitized. Basically the Indians have now done that with the UCEs. It's still basically the same old duffer engine unitized and thrown in some far better metallurgy, electronics and fuel injection. The engine has better performance because of the improved materials which allows for higher continuous RPM ranges.
Actually, the breakin is more akin to modern engines where you just ride it. Avoid high RPM and loads during the breakin time and ride it in the twisties if available so the gearbox gets a workout, too. It needs to be broken in also. I broke mine in most by figuring out where the half throttle spot was and not exceeding it for about 500 miles. That offers adequate acceleration in traffic and reasonable speeds through the gears, I ran mine generally up to about 55 in that period. After the 500 or so just start increasing the speed in steps for the next 500 and by 1000 miles it will be fairly well broken in. This procedure is pretty much what our sponsor, Kevin, recommends. The breakin procedure in the book was never changed from the iron barrel, 4 speed days and just isn't applicable to the new bikes. Basically, just ride it sanely and you will be fine.
Keep an eye on the chain. You will get tot the point that adjusting it every couple of hundred miles is required. It's time for a new one. Get a quality chain from a reputable manufacturer. Get it before it eats your sprockets
Bare