mbkd5, mine came in the big cardboard box as well
. Good idea about changing the oil early, who knows what kind of stuff is in there when they shipped from the factory.
Putting a load on the engine helps to seat the rings, intermittent speeds is also good, no sustained high speed and no lugging it. All stuff that I learned when I had my diesel engine rebuilt on my 3 Ton flat deck.
I really wished that they came with a cartridge type filter on these bikes......
What kind of oil did you use for the break in and what oil ( Manufacture and weight) are you using it her now?
As far as carbs are concerned, yeah these little bikes have pretty sensitive carbs with tiny fuel jets. Keeping any crud out of the carb is just wise and a quick disassembling and cleaning should keep her running smoothly for years to come. I purchased a set of low speed jet ( kit) with different sizes off of fleabay, I may try to experiment with a few different sizes to see if it improves performance.