TOPIC:

Wouldn't painting a case, or especilly the cylinder & head assembly frustrate cooling to some extent?

I'd think the paint would produce some insulative effect...and that the unfinished (rought, unpolished) metal would cool much better.

Paint does reduce heat transmission between the metal and air, I don't know exacty how much. Can't be a huge effect as long as it's thin. With aluminum, you can anodize it to color it and not degrade heat transmission and if it's the right color, it may improve it very slightly.

I was considering painting my engine the same color I am going to paint my frame (Orange) and using polished covers on the sides and top or just sticking to black on the engine. I was curious as to what the effect would be on the heating. Would adding an oil cooler to a painted engine help with the heat issues?

Have had just about every type of paint on a wide variety of Z1/KZ motors over the last 36 years, never a problem.

bountyhunter wrote:

Paint does reduce heat transmission between the metal and air, I don't know exacty how much. Can't be a huge effect as long as it's thin. With aluminum, you can anodize it to color it and not degrade heat transmission and if it's the right color, it may improve it very slightly.

I've always heard that black transfers (or actually absorbs) heat the best.

The effect of paint is practically negligible.

Most of the heat dissipation is done by convection. Air flowing throught the fins, not radiation.

Heat transfer from metal to paint is not very good, but heat transfer from metal to air is even poorer, so air can't keep up anyway even with the paint.


A black body is best dissipating and radiating heat, but only in the infrared spectrum not in the visible spectrum, (what it looks like to us), Nevertheless manufacturers paint engine in black when it comes to cosmetics, so when it comes to only radiation, (motorcycle is not moving), a black engine maybe be, theoretically, a little better dissipating heat. But obviously not enough to make manufacturers rush into painting all air cooled engines in black.

Bad Dad wrote:

bountyhunter wrote:

Paint does reduce heat transmission between the metal and air, I don't know exacty how much. Can't be a huge effect as long as it's thin. With aluminum, you can anodize it to color it and not degrade heat transmission and if it's the right color, it may improve it very slightly.

I've always heard that black transfers (or actually absorbs) heat the best.

Correct. There is a heat radiation effect called "black body radiation" which is enhanced by the color being darker, ie black is best for that effect. I suspect the effect is very small overall.