after 35 years the black paint of the K100 radiator is not so black anymore.
I've been looking repainting the radiator but it seems that the oudside pieces of the radiator are not made from aluminium.
Anyone ever tried repainting the radiator?

thx,M

I haven't analyzed the metal in the radiator, but there are only two metals that I know of being used.  Aluminum and brass.  I think that brass radiators typically had a black oxide coating that was created by a chemical process.  Not sure what was done on aluminum, maybe anodizing.

Paint is not what I would use.  Paint makes an insulation layer that will reduce the cooling capacity of the radiator.  On bricks, cooling is not excessive and anything that would reduce it should be avoided.  Anyone restoring a brick really shouldn't use paint and just leave the finish alone.  On the other hand, if you are doing a custom build, you are probably not going to be doing the kind of riding that would stress the cooling system, so in that case it would probably be okay to paint it.

The radiator is usually hidden behind the fairing or cowl so if you are repainting for looks then use just a bare minimum of black satin and if it is to remain hidden then leave it alone.

I am doing a full rebuild and the result will be a naked bike "cafe racer". So the radiator will be visible and it would be nice to refresh it.
I use special radiator paint. This paint does not build up a thick layer and keeps airflow. Used it before and it works good.
The side walls (collectors) of the radiator are still in good shape and can be cleaned and polished. Only the metal section (middle, top and bottom) needs to be painted.

From what I've seen, most cafe bikes are only used for quick trips around town and don't normally experience the conditions that stress cooling systems, so painting shouldn't be a problem.

mister_anger wrote: The side walls (collectors) of the radiator are still in good shape and can be cleaned and polished.

FYI. it's made of plastic.

that is what I thought.
But my problems have been solved because today I found a NOS radiator for 180$. This is a killer find.
And it includes the thermostat ;-)
And the guy that sells it lives about 20km from my home. So this is really nice.