K11 Owners Group

Gary Bennett · Posted: Fri Nov 28, 2008 9:29 am Post subject: Fix the Heat

I have had a couple of people ask me for photos and details of my K100 Radiator fan install and since it has disappeared from this BB, I thought I would Post it again seeing that there is a lot more interest in it now compared to when it was first posted...

FIX THE HEAT
Stage 1

Due to the introduction of Motronics used on 4 Valve K series, namely K1100RS & LT, some changes were made and not all the changes were successful.

The 3 core radiator used in the K100 series was reduced to a 2 core radiator to allow the fan to have clearance from the much larger air filter housing (difference shown in the diagram below). The less amount of coolant in the system allowed the engine to get hot at a faster rate.

I developed a 3 stage plan to “cool the beast”. Stage 1 was to fit the K100 radiator and modify the factory fan so it would fit in the space provided. Stage 2 was to fit a higher volume, low profile fan and Stage 3 was to fit a Thermo Switch to turn the fan on at a lower temperature as set by me.
Details of Stage 2 and 3 can be found in the post by me called Radiator Fan
Below is how I did Stage 1.

I removed the fuel tank and all the lower fairing panels, which gave me easy access to the radiator. The coolant was drained and hoses removed. There is only one bolt securing the radiator and it is at the top of the radiator, it was removed, making sure that the spacer and bolt are not lost as they will be needed still for the install. The radiator then rolls forward and lifts off the hooks at the bottom.

Three modifications need to be made to the Fan. First change is to cut out one of the two strengtheners to the bottom left mounting bracket as shown in the diagram below. Smooth out any sharp edges with a file as the bottom hose going from the left side of the bike to the right side will go close to this and may touch it, so to eliminate any abrasions will save you any inconvenience in the future.

The second cut should be made as shown in the below diagram, ensuring that enough of the bracket is left so that the bracket overlaps the bottom of the radiator. This will provide the right amount of clearance of the fan to the cores of the radiator (as shown in the second diagram below). Once again smooth out any sharp edges with a file.

The 3rd modification is made to the fan. Using a Dremel or a small hacksaw, cut the bottom edge of the rear cover on the fan away enough so that it gives some clearance to the Air Cleaner housing when fitted to the bike. To assist in this step it may be easier to remove the cover from the rear of the fan, it won’t come all the way off as the wiring passes through the bottom edge, however it does come away enough to ensure no damage is done to the internals of the fan.

Once completed use some cloth tape (race tape) to seal up the open area. I had this tape on my bike for two years and it was still as good as the day I put it on there.

Reinstall the radiator using the spacer at the top, securing the radiator in place on the front side of the radiator instead of behind the radiator as used with the 2 core radiator.

Re-connect the fan wiring and all hoses, re-fill with coolant and replace the tank. Start the bike and get it up to operating temperature and look for any water leaks.

Re-check the coolant level and top up if necessary, replace fairing panels and JOB IS DONE!
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Gary
'94 K1100RS

Beachcomber · Posted: Fri Nov 28, 2008 10:02 am Post subject:

Hey Gary,

thanx for that from this side of the pond.

I'm just in the process of converting my '93 11RS into a "Race Replica" to join my Kay 100 projects.

I bought my 11 VERY cheap [ £500 ] as it was overheating. I traced this down to the stock fan - quick fix.

However, all the articles I've read indicate marginal cooling on the 11. so a rad swap was on the list of "fixes".

I am modifying a Duke 916 fairing for the 100's and 11, so I will take extra care with cooling ducts / flow. At least I know the rad will cope !

Cheers

TJ
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Beachcomber '93 K1100RS / '93 K1100LT and several K100's

Jim · Posted: Fri Nov 28, 2008 1:45 pm Post subject: radiator mod

Hi Gary - thank you for the write up and the pix. Waiting for your other thread with the fan switch mod.

Hopefully we'll hear from others who've done the radiator mod to see how they implemented it.
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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."

dryheat · Joined: 03 May 2008 Posts: 22 Location: Arizona

Are all K100 radiators 3 core or just the 8 valve bikes? Your post implies the switch to the 2 core was made when the change was made to the 16v engine. 89, right? I want to do this to mine as well and not sure if any K100 radiator will do. Thanks

K11Martin · Posted: Sat Nov 29, 2008 3:45 am Post subject:

gary,

Good mod, just the sort of DIY thing which seems to be disappearing with the influx of modern bikes and modern bikers, but I have a question.

Surely mounting the fan on the other side of the radiator will mean that when it starts up it will by trying to suck air through the rad, thus counteracting the Ram-air effect of forward motion and effectively reducing the airflow?

Shouldn't you have reversed the polarity of the fan to make it spin the other way?
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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 Nov 29, 2008 7:57 am Post subject:

Flying Duck · Posted: Sat Nov 29, 2008 12:23 pm Post subject:

dryheat · Joined: 03 May 2008 Posts: 22 Location: Arizona

owrstrich · Posted: Sat Nov 29, 2008 1:28 pm Post subject:

how much for just the 3 core radiator cap...

do you happily accept cash...

Wink

j o
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yeeeeeehaaaaaaa...

Flying Duck · Posted: Sat Nov 29, 2008 3:31 pm Post subject:

owrstrich · Posted: Sat Nov 29, 2008 3:42 pm Post subject:

believe it or not... i have been looking... just went to a marine place a couple weeks ago... you are not forgotten... neither is my evil deed i see...

j o
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yeeeeeehaaaaaaa...

K11Martin · Posted: Sat Nov 29, 2008 6:23 pm Post subject:

Gary Bennett · Posted: Sun Nov 30, 2008 7:29 am Post subject:

That is refering to the spacer on the securing bolt only, not the fan.
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Gary
'94 K1100RS