Radiators/ Overheating

Hey guys,

quick question: I just got back my radiators from meyers after being straightened out. They came back straight as an arrow :bonk: but they are still pretty beat up, I was wondering if painting them flat back before i polish and put on my radiator guards would compromise my cooling at all. I've been thinking about it alot, and feel that my "optical illusion" of sorts will work well, Ijust wanted to get a second opinion before I ruin my recently straight radiators :applause:

Oh yeah, forget to flat out ask my question: will my bike overheat with painted radiators. I've heard from VW mechanics that they powdercoat aircooled blocks on the oldies simply because the powdercoating has a better cooling factor, and can exchange heat quickly.

all views, no replies :bonk: , has anyone tried this? Or atleast tell me what you think. Any feedback appreciated (negative or positive), I just was gonna paint them today ( a break in the weather) but won't unless I get the go ahead :applause:

I can't see how a light coating of paint would affect things too much. Just don't load it on at the fins.

Radiators on cars are painted, at least on older ones and they seem to work fine.

Painting the rads will definitely improve their cooling ability, as long as you don't use 20 coats and gum them up. Any color will do as long as it's not chrome or shiny aluminum paint. The surface color of an object determines its ability to radiate heat.

I do a bit of work in the infrared field and although this doesn't make sense to your common sense, it's true. One property of all materials is it's emissivity or it's ability to absorb heat energy. Colored objects or corroded dull surfaces have high emissivity which allows them to radiate heat efficiently. Shiny surfaces like chrome, polished aluminum or copper have very low emissivity so they don't radiate heat well. Since radiators radiate heat to the air, you want the material they are made of to be a good thermal radiator, dull or painted surface.

An example - 1 square meter of a painted metal surface radiates ( or gets rid of heat, like the bike rad) 587 watts of heat energy at 120 degrees.

The same square meter of the same metal with an unpainted moderately shiny surface has to be heated to 400 degrees to give up the same 587 watts of heat energy.

Any color will do, flat black would technically be the best but the difference may be immeasurable, so pick a color you like. It can be a gloss paint, but not highly reflective like chrome or aluminum. I'm not sure how much it'll lower the coolant temperature, but the painted rads will work better than the non painted. If they are dull aluminum they're already working better than when they were new and shiny.

To test the theory try this home experiment. Take a frying pan that is shiny on one side and dull on the other. The average pan is shiny metal on the bottom and coated or has burnt crap stuck to the top. A teflon coated pan with a clean copper or steel bottom is perfect.

Heat it up on the stove and then pick it up by the handle. Move your free hand towards the dark or teflon side of the pan. You'll feel the heat radiating from it before you get too close. Now move your hand towards the shiny side but be careful. You'll nearly have to touch it to feel the heat. Same thin piece of metal, the dull side is giving up heat like crazy, the shiny side is keeping the heat in. You want your radiators to get rid of heat.

Here's a few Infrared pics of the rads and engine and a few other things.

This last pic is of the aluminum White Bros muffler. My infrared camera sees radiated heat. I can adjust the emissivity level in the camera to get an accurate temperature of shiny metals, but an easier way is to stick a piece of electrical tape on. The tape is black and reveals the true temp of the object. Even though the aluminum is dull, it's still not radiating heat well. The metal appears to the camera to be 85 degrees. The tape shows the true temp is 117. :applause:

Look at a product called GUNKOTE. Manufactured by KalGuard. It is thin like water and needs to be applied with an airbrush onto a pre-warmed surface, and then baked to cure.. I have read that it will improve heat dissipation. I have used it for a lot of projects, and it is easy to work with assuming that you have the correct setup.

Stay away from anything that is so thick that it may act as an insulator. whatever you use it should be airbrushed on, and a very thin mixture.

Yes I remember black body radiation in my engineering classes. It is true the light black coating will improve cooling! :applause:

WR used to come with black radiators, I can't see it hurting...

WR used to come with black radiators, I can't see it hurting...
I asked my mate with his wr400 about his black radiators, he said the previous owner must have did it.

I guess it might have come standard.....

Thanx for all the responses, I'm gunna paint them to tomorrow (weather permitting). I was'nt looking to improve my cooling, just the looks, but thanx to frostbites post it looks like I'll get the best of both worlds. Thanx Guys, (especially frostbite for the info/pictures)


I replaced mine after i bent one up pretty good. I went with the IMS "Works Style" Heavy Duty Radiators from www.brpit.com They work great. Simple to put on.

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