Why Honda triple clamps from the 80's are black

Back in the day, anodizing wasn't as cheap and common as it is today. Raw aluminum corrodes and most manufactures chose to shoot the aluminum parts in black paint and it kept the aluminum from corroding. In the late 80's you started to see manufactures leave cylinder heads and other bits raw. This gave a "factory" look but also was a cost cutting measure. Look back at mid 80's Honda's and you'll see almost all raw aluminum painted black (calipers, master cylinders, engine cases etc). Raw aluminum looks awesome but corrodes. The manufactures jumped on the "coolness" of raw aluminum and saved money at the same time. Yamaha used to paint their YZ side cases metallic silver but I'm sure the bean counters axed that as well.

Anti-glare measure? I thought that was why the 73-75 Elsinores had the painted panel on the top of the tank. You can debate whether it mattered enough to be a genuine problem, given how many bikes were out there with natural/ polished clamps, but Honda's attention to detail suggests they might consider it worth addressing.

Honda stopped doing that after 1984. At least with the CR line up. 85 and on are not painted.

Normally, the bottom clamp was clear coated.

The clamps on my '87 CR250 were clear coated from the factory. They also would clear coat the lower portion of the conventional forks as well back in the day.

Who knew? I never gave it a second thought before you brought it up. I thought it was the same reason we had funny haircuts and uncomfortable tight shorts . It's just the way it was

Most KXs had painted top clamp and bare bottom. Also the cylinder, swingarm and bar clamp were painted.

Bottom clamps are forged aluminum and the top was cast aluminum. On the factory bikes the top clamp was magnesium which corrodes very fast so they painted them. On magnesium engine covers they use Dow-9, which is the gray/brown color.