No offense, but the first video is a series of pictures with no context or explanation, and it's an assembly operation. The second video is an episode of How It's Made, which involves manufacturing from raw materials for the first three plus minutes. How It's Made is arguably a propaganda broadcast about the wonders of American manufacturing (Bosch has manufacturing in the US
); they only show the very highest quality manufacturing processes, some of which are by hand. So you're kind of comparing apples and oranges here.
And here's a video of the assembly process of model engine spark plugs
- also by hand, also in a workshop, just not in as high volume as the Chinese factory.
I suspect that the problems with the LD kit spark plugs are a result of cheap manufacturing, materials, and design, too,
not just sloppy assembly. Pointing the finger only at hand assembly operations tends to imply that people who work in those kinds of factories are somehow inherently incapable of doing a good enough job.
These different spark plugs are also for different markets, in just the same way that a fast food restaurant fills a different market niche than a 24 hour family restaurant, than does an upscale steakhouse. In most cases, the stock plug is good enough.
That it's simple and cheap in the US to replace it with a better plug and get better performance speaks to the fact that the HT engines are designed and built well enough to be easily upgraded.
If all the cheap parts in these kits were manufactured to much higher quality standards, the HT kits would cost twice as much as they do. Motorized bicycles already have a super small niche because of 50cc scooters; increasing the price of the kits would make them unsaleable.
Sorry about the rant, but I get aggravated when people point fingers about quality. The picture is so, so much bigger than some decent people with jobs assembling things.