Further to the issues Rob, (who promises to be along SOON! Hint, hint Rob...), has been having with his K1 heat generation...

I've seen posts on here relating to "2 row" radiators and "3 row" radiators.

So, the question is, which bikes have which radiators and how do you tell the differences? Max BMW parts fiche seems to have the same part number spread across the range from K75 through K1 to K100 to K1100.

Confused of Middlesex.

I know a little but not all the details you seek.

The 3 row was used on very early K100 models, I can't tell you when they stopped.

They are easy to pick apart visually, the edges of the core on a three row are parallel to each other and match the tank width. A 2 row is narrower and parallel in the centre of the core but bulges out at the ends to match the shape of the end tanks.

Al

Dear confused from Middlesex
the 3 row core was used on 83 and 84 and seeing as the 2 row replaced the 3 row the parts fish will tell you only a part number for a 2 row as the 3 row no longer is available.
If you are considering a 3 row because a standard bike is overheating you are barking up the wrong tree.
A 3 row is only really needed if you are carring a bigger than normal type of load. I use a 3 row core because I tow a heavy camper trailer and AL uses a 3 row because it was there and he has a chair.
With a big load and slow going a 3 row will cool faster when the fan comes on and will help on a very hot day.
Your mates K1 is overheating then look futher because if you go to a 3 row it probably wont solve the problem. The reason for the overheating is still there and will eventually rear its ugly head after it cooks an engine.

Thanks for your quick answers folks!!!

The K1 isn't overheating as such. The problem is that, in the current very warm weather here, the heat from the engine is enough to toast the rider's legs in a very short time, and worse when the fan kicks in. It's not fitted with the optional/aftermarket deflectors in the fairing, which doesn't help a lot.

Last night we had a squint at the radiator cap. It seems to be a bit deficient in the plastic department. Comparing it to the one on my K1100, there wasn't a plastic "retaining" clip on in it, and there was a rogue flat rubber washer that appeared to seal the hole that lead to the overflow bottle.

After removing that, we ran the motor up until the fan kicked in. We could see that coolant was now flowing into the overflow bottle, which had never been seen before. And the level went down there when the bike cooled too ;-)

A new radiator cap is in the offing, at least.

I use a 3-row on my '92 k100 just because it makes me feel a little more comfortable.  My bike wasn't overheating really, but was running a little warmer than I thought it should on a cold day.  Ever since I put that 3-row in there, it runs a consistently good temperature just below the half way mark on the temp gauge. This had nothing to do with rider heat though. The bike is designed, and has to, run at a certain optimal temperature, and that's whatever the stock thermostat is (85C I believe), so unless its running pretty far above that usually, rider heat is going to remain the same.

The 3-row radiator is different from the 2-row in that it is 50% thicker.  It can be somewhat difficult to tell unless you view it from the top or the bottom.  The sides are the same width between the 2-row and 3-row.  On the two row, the fins are flush with the sides in the front, but then the sides extend maybe a couple centimeters back farther than the fins / tubes go.  The 3-row fins / tubes are flush with both the front and the back.  Here's some pictures:

2-row:



3-row:

The K radiators last exceptionally for an aluminium init. I have a BMW 320i car and it is now on it's 3rd unit in 19 years and both the other units developed corosion leaks the 1st at 79000km and 6 years the next at 180000km and 18 years and all the time the coolant was kept in good order and changes as per schedule and the same for the Ford Fairlane I got rid of recently, it went through them even quicker.

My guess is the two or three row radiators may not reduce the hot leg feeling because two or three row they still have to shed the same amount of heat which then ends up on your legs. I think the heat problem is better addressed by insulation, there have been a couple of threads about this over the last few years.
Regards,
K-BIKE

Just gathering up the spares I'm dragging back to OZ with me and noticed more clearly that the three row radiator is OEM part number
17 11 1 460 490. It's shown in one of the pictures above (11460490 on the sticker), as well, in case anyone's attempting to hunt one down. Alas, they are truly unobtanium from Bay Em Vay and any effort to order one from the factory will only get you a superseded part number, two row and some measure of disappointment, not to mention a large hole in your wallet where the money used to be.

I did locate all of the rubber shrouds which sit round the injection rail, etc., as well. This and the fuel hose insulation trick should help alleviate the dreaded heat shed against the rider's legs whilst stuck in stop 'n' go traffic.

The hardly-used three row I bought for US$40.00 two years ago from a mate came with a new (bagged) 85 degree thermostat, seal and all of the rubber bushes and mounts. Me thinks OZ (and perhaps the Sahara, Nevada's highway 50 in the middle of Summer, or LA rush hour) is the perfect place for a it.

I have a 1996 K1100LT dragging a chair which has a 2 row as standard & no overheating problems, but I do not ride very often in the summer months.
I have 2 3 row on the shelf, they come off the following,
a K100 1983 & a 1986 K100RT.
If any one needs one give us a yell, both are well used with some minor fin marks.
I also have a K100-1983 frame, straight & never broken, 200,000 KLM as a solo
& another 150,000 KLM with chair fitted.
It has solid front engine mounts, not rubber as per all RS & RT & LT
free ( or a drink or 2) to a good home, pick up from Gladstone SA.
grandad

keefk1100lt wrote:Thanks for your quick answers folks!!!

The K1 isn't overheating as such. The problem is that, in the current very warm weather here, the heat from the engine is enough to toast the rider's legs in a very short time, and worse when the fan kicks in. It's not fitted with the optional/aftermarket deflectors in the fairing, which doesn't help a lot.

Last night we had a squint at the radiator cap. It seems to be a bit deficient in the plastic department. Comparing it to the one on my K1100, there wasn't a plastic "retaining" clip on in it, and there was a rogue flat rubber washer that appeared to seal the hole that lead to the overflow bottle.

After removing that, we ran the motor up until the fan kicked in. We could see that coolant was now flowing into the overflow bottle, which had never been seen before. And the level went down there when the bike cooled too ;-)

A new radiator cap is in the offing, at least.

I think you are on the right road keef

good luck

it does seem problematic in cooler climates as the ambient temperatures increase ....I guess many do not experience this ...but for commuters ill bet they are very aware of the issue ,,,,it seems to me that until about 25 c the cooling characteristics are fine (for a engine developed in the northern end of Europe) .....
to all those south of that, like spain usa aussie and many others
can I offer the comment that until it gets over that magic temperature the ride is always clean and cool as

a note, I did a radiator thermostat upgrade with an aftermarket unit  which proved to be a positive result
from that investigation I might comment that the thermostat unit could seem to be an issue ....although maybe unnoticed until heat issues occur .....I suggest look there first , I found that the throw (passing of fluid ) was quite restricted on a couple of units I tested as it wouldn't throw to full open as temperatures were reached ,
 this has a compound effect  1> the bypass flow around the radiator (designed for quick heating to operating temperature )   does not close fully as the thermostat reaches flow temperatures (resulting in bypass hot fluid being recycled bypassing the radiator . consequence being that the radiator is holding back high than normal temperature fluid
2> the full flow through the radiator is not realised when running relatively hot temperatures . thus the cooling effect is dramatically reduced

good luck

some where to start huh ?

Pleased to be back here in my new persona!

And also delighted to report that a new radiator cap sorted out Rob's overheat problems as well as mine