Cooling - Radiators, what is everyone using?

[RC45]

The bike currently has a ZX7R radiator. What various options have others used on their replica builds. Can anyone grab a stock RZ radiator they may have and take a quick height width & depth of the finned core section?

The ZX7 one has a pretty large volume. 13.25"x12.5"x1". Curved and all modern looking. Maybe too modern.
Its more 1992 than 1982 in appearance.

So I was thinking of something more period looking, like this late '88 or '89 TZ250 reverse cylinder unit.
13.5"x8.5"x1.25". So roughly 78% of the volume and surface area of teh ZX7R unit - but is more in keeping with the theme.

1990 ZX7R Radiator






Reverse cylinder TZ250




Overlay comparison

[MK]

By any means, stay with the rad you have.

The stock RD500 rad is by far too small and anything bigger does the job better.

[RC45]

I forgot I had a box full of actual GP500 radiators. Found this mid 1980s one - , I think its an OW86 YZR500 unit. It is the most retro looking The others are all curved like the ZX7 unit. Those I think are from the RGV500.

I need to see today if there is clearance for this and retrofit larger inlets tubes. I think they kept them small diameter to up the flow rate of the GP radiators.
14.75"x8"x3" gives 2.1 x the volume - thats a lot of extra coolant!
I am guessing I may have too much cooling with this one though.

[lost1750GTV]

"I forgot"
You must have a lot of stuff!
"Too much cooling"
Cover part of it , as needed.

[RC45]

"I forgot"
You must have a lot of stuff!

Sadly, I do. Crates and boxes and storage lockers. Not sure why, but I have 7 TZ250 frames - ranging from 1986 to 1996. I figured I may need one and they used to be so cheap from Japan. Same with TZ250 swingarms - 10 of the bastards kicking about.
In the last 2 years TZ parts have really gone up in price. I think I paid like $200 each for the frames and probably $150 each for the swingarms over the years - now are closer to a $1000 each opening bid. Not really worth buying on a whim at those prices.

"Too much cooling"
Cover part of it , as needed.

So I did some reading on radiator core thickness versus frontal surface area - it seems the bigger thinner radiators are more suited to slower speeds and the thicker smaller radiators are better suited to higher speeds.

I think I will give the YZR500 radiator a try.

[lost1750GTV]

"Sadly I do".
Nah, that's a good thing if you've got the room etc.
Sad is what I sold a tz700a for (ok, I bought it just as cheap), or that I sold the 250j at all.
And ......

[rz500guytexas]

Rick's auxiliary radiator would do it. You just have to engineer, fabricate, and re-pipe it. No idea who he had build them. Never overheated on a 100 degree track day.

[RC45]

The ZX7 radiator was more than sufficient previously, I just wanted something more period correct looking.

[alkmist]

Hi RC45. The project bike I purchased also came with one of those ZX7R radiators but no fan. Did your bike have the complete radiator assembly- Heat exchanger/fan/shroud/electricals etc?

[RC45]

The current install doesn’t use the fan as no space for one and
its a pretty big fan. I have the fan, thermostat switch, radiator mesh, bolts and clips here.

[RC45]

I have had to switch to a 4TW TZ250 radiator - there is just no way the ZX7 radiator will fit inside the fairings properly.
If need be there is place to add a second TZ250 radiator .

[SPCylinder]

I can't understand how an RD 500 rider, (I don't mean a motorcycle hiker and flower picker) could find the original, or any other cooling system for the messed up RD 500 engine to be sufficient?
The RD 500 engine is an absolute crap in the whole, and especially in the cooling!!! e.g. -1,9 litre coolant for a 500 2-stroke, such an absolute crap!!!
This tinkering, because construction can not be said for such a bastard of engine, this one has been created in a state of complete intelligence liberation. A peculiarity and an unprecedented bungle in a 2-stroke, is the upper cylinder head, where this ignorant tinkerer, -for a 250 engine - has a -!! - 14mm inner diameter -!! Steel tubes, for the coolant (hot) outlet provided!!! Is that bullshit, or...????
For the RD500 engine, or rather for these two 250 engines, every change - no matter if it's the size of the radiator surface or the coolant quantity -and and and and ... ...a gain in all areas, and whoever doesn't want to understand this is (in my opinion) beyond help.
But I don't want to offend or instruct anybody and I don't want to discriminate against other views. I write here as an owner of some RD and from my very long experiences with 2strokes and especially since 1984 with the Crap birth, RD 500LC, until today.

[RC45]

I think I am close to the final layout of the new big bore TZ250 radiator layout.