Background: Finally decided to get off my duff and start working the K100 project I picked up last spring. No idea how many miles on the bike as the seller wasn't exactly straight about any or everything. I got that message when he stated that the only reason he was selling was that he needed to make his bail money. Seems he had fallen off the wagon and waved a pistol around when the new owners of the building where he had been super for years took over. But the bike had sat  in excess of 5 maybe 10 years in the 1st floor garage of that apt building in Berkeley Ca and was in a sad state of repair. Before starting the restoration I did get the bike to fire up briefly but did not ride it as that looked a tad dangerous. Tires and brakes were questionable. I took the frame off along with the front wheel and left the engine and rear wheel on a trolley. Had the frame powder coated and have begun reassembly. For some reason known only to the previous owner he had cut 4 wires in the main electrical harness just before it enters the headlight. So I spent an hour or so replacing his jury rigged wiring with my jury rigged (but soldered) wiring and sealed the cable cover as best I could. Now I want to begin reassembly of the frame and engine so I can work on a piece at a time. I figure it will be winter before I get much further and it's best to be able to wheel the machine around a bit. Suspect I'll build a tent around it so it will be out of the weather and accessible. The garage being full of K75's and such.

The problem: I'm ready to start the reassembly but need to get the radiator re-mounted and all the hoses connected up. But the radiator is in sad shape (as was the whole bike) and many of the aluminum fins are damaged, bent back or disconnected. As near as I can tell the radiator doesn't leak.  At least not in my cursory testing. But who knows. Any advice or comments about reworking a K100 radiator. Is there any reason not to? I've been trolling the net looking for 2nd hand radiators but so far haven't found any.

All polite comments and advice appreciated.

Wouldn't use the old radiator, better throw a question here;

https://www.k100-forum.com/f31-parts-needed

Arlina wrote:Wouldn't use the old radiator, better throw a question here;

https://www.k100-forum.com/f31-parts-needed

Well I did look at that. Also I compared the K100 radiator to a K75 one and they are different in physical size. So I'm trying to follow the conversation of 3 row vs 2 row and discern which is appropriate.   Not to mention that the aluminum one is  out of stock at the moment.

Thanks

I doubt that anywhere in the US is (currently) hot enough to warrant trying to find a three-row radiator, unless you decide to move into Death Valley AFAIK BMW stopped with the three-row radiator after a couple of years as the two-row one is surprisingly efficient.

BTW I love that R-series fairing. It absolutely suits the bike. I get tempted to try it myself every time I see your avatar...!

Use 2 or 3 row as you find them. But one point I am not sure of is if K1100 94 on radiators fit the K100 as there is a frame modification up front. K75 front down tubes differ so it doesn't fit.

On the headlight, take the opportunity to fit a relay near the headlight and get a ceramic bulb holder and that solves your issues there.

the k1100 radiator wont fit directly but it can be modified to fit , fred has one now , which helped with aftermarket fan fitment 


the 3 core radiator does a better job at cooling whilst travelling above 100kph but if your in traffic or slow moving its just more hot fluid in front of the rider to burn your legs 

id recon the 2 core radiator was released as a partial fix for reported heat issues everywhere else in the world that achieves over 20 c for long periods of the year  .and is a good choice

Well, that's it for the moment guys. Thanks all. Called my buddy, Greg, whether he had one. He did so I went over to look at it today. His matched the one I had taken off, no fan or rubber bits but the fins looked to be in much better shape which is what got me started on this quest. Asked what he wanted and we settled on USD $20.  Then just as I was settling down thinking that wasn't too bad he brought out this YSS rear shock with less than 3,000. miles. And then his Australian shill showed up and they team tagged me so I'm also out $200. for an almost like new shock. I tried to say NO! but it is so pretty. Sucka for a pretty face - I guess. Made in Thailand apparently. Guess I'll go and watch that video of "One Night in Bangkok" and dream of pretty Thai's.

Now can anyone explain 2 row vs 3 row to me? I've looked these radiators over and am in the act of straightening fins at the moment but haven't clued as to what that descriptor is about.

best regards
J.

Nice. Did ya hurt your hand getting it in your pocket for the money that fast!    Glad to hear the radiator stuff is working out.

jjefferies wrote:

Now can anyone explain 2 row vs 3 row to me? I've looked these radiators over and am in the act of straightening fins at the moment but haven't clued as to what that descriptor is about.

best regards
J.

3 versus 2. Both radiators have the same plastic side tanks but the 2 core has 2 rows of coolant tubes running  between the plastic side tanks while the 3-core has, you guessed it, 3. As a result the 2-core isn't as thick.

And by the way, that black foam piece that sits across the top of your 3-core won't fit the 2-core due to the different shape of the rad. I believe BMW dispensed with this foam "gasket" when the 2-core was implemented. I'm sure you could modify its shape though.

RS Rider wrote:

jjefferies wrote:
Now can anyone explain 2 row vs 3 row to me? I've looked these radiators over and am in the act of straightening fins at the moment but haven't clued as to what that descriptor is about.
best regards
J.

3 versus 2. Both radiators have the same plastic side tanks but the 2 core has 2 rows of coolant tubes running  between the plastic side tanks while the 3-core has, you guessed it, 3. As a result the 2-core isn't as thick.

And by the way, that black foam piece that sits across the top of your 3-core won't fit the 2-core due to the different shape of the rad. I believe BMW dispensed with this foam "gasket" when the 2-core was implemented. I'm sure you could modify its shape though.

Took me a while, but by dint of struggling I think I understand. There are 17 rows of tubes running from side to side and each row has 3 coolant tubes - if what I'm looking at are coolant tubes. Ok that makes sense. I'll pull the K75 ones down and check them. But I don't find any foam "gasket". But as I said the bike has been seriously abused.

And another question. I tested the fan. It worked but squeaked/squealed a bit and so I replaced it with a K75 one. Issue as near as I can tell is that after sitting for 10 years or so the lubricant has gone off a bit. I was able to apply a bit of 3-in-1 on the back side of the fan motor. But getting to the front was nigh near impossible. So I squirted WD-40 up there and tried to position the piece so it would drip back down. But has anyone pulled the fan motor apart and lubricated the bearings? Is it as bad as it looked to me? If not impossible I have two spares that I could be putting in the line to be cleaned and worked up for any eventual failures.

They all fail eventually as they are not of very high quality. In the tech pages via the Portal there is a write up on fitting a SPAL fan and that will be a big improvment.

RicK G wrote:They all fail eventually as they are not of very high quality. In the tech pages via the Portal there is a write up on fitting a SPAL fan and that will be a big improvement.

I might be trading my K75S for a K1100LT, with the dreaded heat-to-the-rider issue. Will the SPAL move the air past fast enough to improve that, or neutral effect, or worse? I would be doing a lot of riding in the heat of the day... will mostly be my rainy day (well night, since I work mids) commuter, but I have heard the stories!

Dan Pete wrote:Will the SPAL move the air past fast enough to improve that, or neutral effect, or worse?  

The Spal fan will likely have a neutral effect because the fan's purpose is to moderate the engine's operating temperature, not the rider's. The Spal is desirable because it is more efficient and more robust in construction than the OEM fan.

Heat radiating from fuel within the fuel tank seems to be a large source of rider discomfort on Bricks, especially those with full fairings. Fuel coolers of various configurations and deployment of a johnny blanket seem to successful at lessening that heat. Other mods can be found in the Heat Management document on the Tech Page within this site's Portal.

Since the fan only runs when you're idling or stuck in traffic it will have a minimal effect on rider discomfort at speed. As mentioned, the OEM fan is not the highest quality and falls prey to many problems. They usually start as sticking bearings and end with the blades moving forward on the shaft into the radiator causing leaks or melting the brush holders when the bearings seize solid.

Many owners have done the Spal retrofit, I've done two myself. With the radiator out of the bike it's an easy one hour job. As long as you are doing it, it's not a bad idea to install a manual switch to override the fan control unit when you're stuck in traffic on a hot day.

I would also suggest doing a white distilled vinegar flush on both the insides and the fins of your radiator. It will get any mineral deposits out of the passages and the dead bugs and dirt out of the spaces between the fins. It made a big difference in the cooling on a couple of my bikes.

Point-Seven-five wrote: As long as you are doing it, it's not a bad idea to install a manual switch to override the fan control unit when you're stuck in traffic on a hot day.

Curiosity, but is the manual switch to turn the fan off or on when you're stuck in traffic?

jjeffries wrote:. . . is the manual switch to turn the fan off or on when you're stuck in traffic?

The manual switch would turn the fan on when you're stuck in traffic. It's a comfort to those with expectations that decades-old BMW relays and sensors could fail to activate their moto's fans when necessary, resulting in mechanical chaos, broken dreams, personal despair and financial loss.

Make sure all the baffle pieces that are supposed to be inside the fairing are in place. They make a difference.

A fan override switch is easy to do. I used splice connectors and tapped into 15 (green/brown) and A2 (violet/yellow) wires coming out of the back of the temperature switching unit in the relay box underneath the seat. I then ran two wires to an unused rocker switch next to the ignition switch.


Particularly useful if stuck in traffic and going nowhere for an extended period. I switch it on and it holds the needle in the temp gauge in the middle until I get rolling again.

While not terribly useful where a traffic jam consists of a dairy cow loose on a dirt road, the fan relay override allows the rider to activate the fan BEFORE engine temperature reaches 100C. This helps keep the engine temperature(and the rider) a few degrees cooler as one inches past a highway construction project or the cop blocking traffic while he investigates a minor fender bender at rush hour.

Point-Seven-five wrote:the fan relay override allows the rider to activate the fan BEFORE engine temperature reaches 100C. This helps the rider keep a few degrees cooler as one inches past a highway construction project or the cop blocking traffic while he investigates a minor fender bender at rush hour.

Unless that fan is blowing air across ice that then travels up ductwork into your skivvies, you'll still be hot until you start barking at the sun, strip off your gear and get doused with 44oz Slurpee while your thighs and crotch are being transformed into pizza warmers during the slo-mo parade, if you're the sensitive type. 

You Guys! Always thinking of how to make it worse^B^B^B^B^B better. I'm out replacing the steering head bearings. Pound them out  Pound them in. But the frame looks so pretty in its virgin powder coated shiny black.

charlie99 wrote:the k1100 radiator wont fit directly but it can be modified to fit , fred has one now , which helped with aftermarket fan fitment

Is this true?? I was under the impression the 1100 radiators were a straight swap, I've fitted a rad that was sold as such to my 8v K100 with no problems..