K11 Owners Group

Flying Duck · Posted: Thu Aug 28, 2008 5:20 pm Post subject: Thicker radiator?

I'd like some input from those who have installed a 3 core radiator. Does it make a noticable difference in lowering the heat? RS? LT?
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

Moondog · Posted: Thu Aug 28, 2008 5:37 pm Post subject:

There are some threads around and it seems to work. Installation needs a little modification. I believe the three core is off the K100. I might try it next year. Finding one might be a bear.
_________________
"Badges? We don't need no stinking badges"!

I like the social aspect of riding. Rally's, socializing, drinking beer, fartin' and carrying on. Smile

2004 R1150RS
1996 K1100RS (moved on to new home)

duckbubbles · Posted: Thu Aug 28, 2008 8:31 pm Post subject:

I still run the original 3-core radiator in my 1100 hybrid. The temps run about 90-110 deg above ambient. I also run the stock, and original, thermostat. Even in 100+ deg, if I have my fan on, it will rarely run over 200 deg. I have a direct reading temp gauge installed, meant for a car.

If you can find a good one, it is worth using.

Frank
_________________
85 K100/1100RS, 321,000 miles, 25 years
96 Ducati 900SS/SP, sold it
05 R1200ST, 35,000 miles, 5 years
400,000 BMW miles

Flying Duck · Posted: Thu Aug 28, 2008 10:54 pm Post subject:

What mods are required?

By the way. I initially used a 6ohm load resistor in my fan switch circuit. Changed in a 4 ohm which gets the dan running at a higher speed but not obnoxiousy loud like full fan operation. Did that to the RS - gonna do the LT too.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

michaelcurrin · Posted: Fri Aug 29, 2008 8:38 am Post subject:

Drake,

I've been running a three core radiator in the RS sidecar rig for a while now. With the old radiator the temperature gauge spent a lot of time in the red while riding, especially in the mountain where I spend a lot of time chasing Hayabusa and ZX-14 sidecar rigs.

WIth the three core there is a noticeable difference in the temp gauge.

I remember I had to trim a little plastic off of the back of the fan housing so it would clear the air box. I covered it with duct tape.

On my rig it was kind of a pain because the sidecar subframe runs in front of the radiator, should be fairly easy on a solo bike.

There was a thread with better instructions and pictures that I went by.

Mike
_________________
Mike Currin
20 BMW R1250RS
93 BMW K1100RS / EML Speed 2000
06 Ducati ST3
67 Triumph 650 chopper

Moondog · Posted: Fri Aug 29, 2008 2:15 pm Post subject:

Flying Duck · Posted: Fri Aug 29, 2008 2:24 pm Post subject:

So my real question was not how hot the engine is but how hot MY LEGS get.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

Moondog · Posted: Fri Aug 29, 2008 2:34 pm Post subject:

michaelcurrin · Posted: Sat Aug 30, 2008 9:59 am Post subject:

hockeyshifter · Posted: Sat Aug 30, 2008 1:09 pm Post subject:

of course this is a long standing heat issue .. will a three core help yes but only under heavy loads the flow of water is controlled by the thermostat. if you want a quick cheap fix take out the restrictive thermostat. most cars only use a 2 row. and some large truck will use a 3 row .. note: the water jackets in the engine are really just keeping the cyclinder sleeve cool not the head or the crank or the piston etc .. if we want to shed the heat the bike needs an oil cooler.. oil is the only fluid that makes direct contact with all the metal in the case.. with oil that is cooled the heat transfer would be much greater and the effect of keeping the unit cooler would be signifent . most heavy trucks have three oil temp gauges on the dash . oil ( for the turbo), transmission , and the drive axle. oil that heats up past a certian point becomes less effective at lubing the components and there for accelrates the wearing process.
The main issue is the fact that these bike just do not handle stop and go traffic very well. As riders we are being cooked to a nice temp of 200+.

my suggestion would be a follows.
1- install exhaust wrap.
2- get the oil filler plug that has the temp guage built into it and montier that way. (a&s cycles)
3- remove or alter thermostat so that more fluid flows through the radiator. (note drilling small holes in the baffle will improve flow my father did this on a piper cub he flew in the desert )
4- set up the fan so that it is always spinning; that way air is always passing over the cooling fins
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fix the problem not the blame ; fix what is messed up ; NO one is to blame.

duckbubbles · Posted: Sat Aug 30, 2008 4:23 pm Post subject:

I also think that the K1100RS type of lower fairing is worse as far as putting the heat to the rider. The early K100RS type fairing lowers have much more place for the heat to exit and don't cover the lower engine. But the K11 fairing looks better.

Frank
_________________
85 K100/1100RS, 321,000 miles, 25 years
96 Ducati 900SS/SP, sold it
05 R1200ST, 35,000 miles, 5 years
400,000 BMW miles

acftfliehr · Big Brick Rider Joined: 05 Nov 2007 Posts: 62

Hi everyone, I had to get my 2 bits in on the radiator 3 core vs 2 core.

I have ridden my K100RT since 1985 in Southern California to include places like Death Valley in the Summer (just passing thru) with temps in the steady 120-degree mark. The K100 gauge (no numbers) while at speed while a wee bit above normal at 140K (about 85MPH). This bike I still have and have around 250K on the clock.

Heat was bad on my lower legs but the louver mod greatly improved the riding comfort and I think at speed, helps produce a venturi effect in savaging the heat thru the normal lower openings of the fairing.

Recently I delved into the K1100LT and noticed the Temp would increase while riding up a grade with lower 90-degree weather, and I mean increase as I added power and speed. At 90MPH the temp would go close to the red and as I backed off, temp would go down, I would have not liked taking this beast out to the desert.

I swapped radiators after reading about someone’s success in the tech forum, and now the bike runs like my old K bike.

Body temp is the same however as the heat is still rolling over the body. I have tried using 4" computer fans in the exit holes of the lower, which seems to help a bit, will try to use 4" radiator fans in the future. They look cool with their red led lighting however and a sheriff on a Harley pulled me over recently and asked me what the red lights in the engine was?!?

I took the old 2 core radiator down to a radiator shop and had it inspected and flushed, etc.. They found the unit as good as new.

I installed it into my 1985 k-bike with a new thermostat.

When driven in the hot weather, it did the same thing as the LT did!

I removed the thermostat entirely....

It took longer to warm up in the morning, to be expected, but on the way home from work with temps at the lower 90's there went the gauge.

I don't know if these bikes would've ever overheated, because where the temp probe location is at the water pump and not the head, where it really needs to be to get accurate measurements and damage warnings.

I just don't like any indications of climbing (or dropping) with no known cause.

I then bought a 1985 K100RT that a guy couldn't start for $700.00, (new Radiators go for 800.00+ now just to get the 3 core unit.

With that radiator on, K100 is back to normal.

For comfort I think the louvers are the trick, but I still plan on playing with exhaust fans in the lowers, that might be the way to go along with the Johnny Blanket, which I have yet to do.

BTW, I am parting out the 1985 bike… Duck, can we talk?

Also, spoke with a radiator shop in the Phoenix area, they said it sounds like the radiators are inadequate, and want to help me develop a better unit, they also said that “Water Wetter” and similar snake oils do work, in that it reduces emulsification in the head areas and they have seen a reduction of 50 degrees F using the products in race engines.

I also saw a guy that put an after market fan on his bike either here or the flying brick site, but lost the trail, this shop also uses hi-tech fans that have greatly evolved over the BMW fans that we have. (Quieter, more airflow, brushless and higher reliability).

Gotta go, wife is pissed I am on the computer and into my passion, maybe I should switch to porn!?!

Jim · Posted: Fri Sep 05, 2008 10:48 pm Post subject:

I think an after market brushless fan would be the way to go. I am going to do the fan switch mod in the meantime.
_________________
Jim
1997 K1100LTSE 94,000 - still has gremlins!
1995 R100RT Classic 16,650 crashed - repaired!
1992 K75RTP 46,000

"We shall not all die, but we shall all be changed."

Flying Duck · Posted: Fri Sep 05, 2008 11:13 pm Post subject:

johnpeter · Joined: 14 Aug 2008 Posts: 20 Location: Los Alamitos, SoCal

K11Martin · Posted: Sat Sep 06, 2008 3:16 am Post subject:

To simplify Johnpeter's post...don't remove the thermostat as a means of making the bike run cooler...in hot climes it will probably make it run hotter!

In a typical car, if the engine is overheating, a simple way of cooling it is to run the engine at around 2000 rpm with no load. this gets the water pump working, and circulates the water through the radiator, where the fan can do it's job and blow air over and through the fins.

Try this with a K1100 and it has the opposite effect. As the revs increase, so does the engine temperature, primarily because the extra heat generated by running the engine faster cannot be dissipated as the fan doesn't run fast enough to cope with the excess flow of hotter water without assistance. It needs the extra air flow from vehicle movement to achieve satisfactory cooling.

Removing the thermostat will permit the water to flow much quicker around the engine and this could easily cause overheating rather than cure it.

The best way to effect a cure is not to use a larger rad (as this will cause overcooling during colder weather) but to do as Duck has done and make the fan spin faster. OK, this may possibly shorten the life of the fan, but it's my bet that BMW have engineered in sufficient headroom to cause this not to be a major cause for concern.
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Currently riding a '93 K1100LT (ABS1) decked out with lights and aerials (Ex 70's Vespa rider)

Why not join the UK owners club at http://forum.bmw-club.org.uk/

Gary Bennett · Posted: Sat Sep 06, 2008 10:01 am Post subject:

I have done the K100 Radiator mod (i'm the one who posted all the photos on how to perform this mod) and it makes the K11rs run as cool as a K100, which is noticably better. As for overcooling, that's just rubbish. The thermostat, if operating correctly, will maintain the engine temperature at at the degrees that it was designed to open at.

Simply speaking, the thermostat maintains the engine temperature by opening and closing. The radiator just cools the water, thats it. If the radiator's efficiency isn't good enough, water that hasn't been cooled enough will be finding it's way back into the engine, which will send your temp gauge rising. If the radiator is too efficient (too big), the thermostat will simply open and close to maintain the correct operating temperature and that is exactly what they are designed to do.

My temp gauge rises and falls just like they do on a K100 and I won't stop modifying until I can get the guage remaining stable.

The installation of a K100 radiator is the first thing you should be changing, as it is bigger than the K11 unit.

The next thing is to change the thermistor that decides when the fan is turned on and off. The factory one turns the fan on way too late and cuts out too early. I have purchased an electonic kit from Jaycar (Australia) which will (when assembled) allow me to decide what temperature the fan will cut in and what temperature it will cut out. Radioshack should have something similar for you guys in the States.

The installation of a higher volume fan (as suggested by K11Martin and others) is a good idea and should be the next step after the new thermistor is fitted.

After the above 3 steps have been completed if my temp gauge is not stable in stop/start traffic and highway use i will install an Oil Cooler as this will lower the core temperature of the engine. If your engine oil gets too hot it is damn hard to cool it without the help of an oil cooler, thats why K12's have an oil cooler.

I am up to the Thermistor stage and I have fitted a manual override switch to the bike until the kit is assembled, installed and tested.
K100 thermistors turns the fan on much sooner than the K11 unit, but it can't be used on the K11 as they are not compatable with the Motronics.
_________________
Gary
'94 K1100RS

Flying Duck · Posted: Sat Sep 06, 2008 11:02 am Post subject:

Gary Bennett · Posted: Sun Sep 07, 2008 10:31 am Post subject: Re: Thicker radiator?

Flying Duck · Posted: Sun Sep 07, 2008 11:10 am Post subject:

I did the fan swtich thing because I was in there and it was relatively easy.

I wasn't attacking people who had done the 3 core mod, just trying to justify to MYSELF if it's really worth the effort which is why I started this thread. If the point is to make the engine run cooler and last longer then I really don't see the point since the engines are pretty bulletproof from the get-go. As stated, my objective is rider comfort, not engine longevity or having the engine run in the "perfect" temperature range. But those are just MY priorities. We all have different priorities - who is to say who is "right?"
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE