So these radiator fans are crap.

[mjydrafter]

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I kind of knew that my fan was junk.  I could spin the blade by hand, but it was really stiff.  Further inspection revealed that the fan blade was just spinning on the shaft and the shaft was not turning.

I had the fan and radiator that the PO had replaced prior to me getting the bike.  So I inspected that as well, FUBAR'd just like the current one.  This one had done the popular number of drilling into the back side of the radiator and ruining it.  Stupid design.



Both fan motors besides being stuck fast, had the at least one of the brush holders completely melted, and not operable.

I did a bit of research and decided that replacing the crap fan with the same crap fan was silly.  I found a few posts here and there about what could be used in place of the original fan.

What I found was that the Spal 6.5" puller fan was a good option.  Just fab up a bracket, soldier the BMW fan connector on and we should be good to go.








I made up the bracket, and attached the fan to it.  I covered the screwheads and back of my bracket with some cork gasket material, so nothing should rub.

I decided that the K100 Radiator, although I can't use the stock K75 radiator surround, is the better bigger radiator.  The 75 radiator must be a 2 or 3 core vs. the 100's 4 core, it is thicker.

Most of the documentation I found said that you must remove the radiator to remove the fan.  Now I must admit, that my bike being pretty naked is already pretty easy to get to the radiator.  I removed the tank (more on that later), I removed the air box top, and the intake that goes up to side of the rad.  Then I removed the top rad. bolt and took out the 2 bolts holding the radiator fill and hose.  With those removed I could move the rad. off of the bottom mounts.






Now, the fan does need to be taken apart on order to remove it without removing the rad.  So first free the fan bracket, then hopefully your fan blade will be easier to remove than mine.  Remove the fan blade, then the back cover of the fan motor.  Flick the fan mount spring clips off, and it will all come out in pieces.  Your hands may not be the same for a while afterwords, but it'll come out.  :yes

I would assume the K100 wider rad. afforded me extra room to remove the fan and bracket.

I was able get my new fan and bracket put back in without any additional drama.  You must wiggle it a bit getting it into place but no worse than any other parts.  Since I used the original fan bracket to make up mine the fan fits right into place pretty easily.  I ripped the rubber cushion/bushing on the upper mount, but this was actually a blessing as it made reassembly much easier.

I also took this time to insulate the fuel return hose and I also added my version of the Johnny blanket.  I used the foil lined bubble wrap insulation.  I also made my fuel return hose insultaion tube out of the same stuff.  I used a strip of the isulation about 1' wide by 4' long.  I just laid it in with a small slit up near the steering bearings, and  holes for the the fuel tank rear mounts.  One extra hole for the fuel pump electrics and ran it back just past the tool box above the computer.  It made a noticeable improvement in the under seat & tank heat issues.   

[Lawrence]

Great info!  Thanks for taking the time to educate us on our options. 

[TimTyler]

... I did a bit of research and decided that replacing the crap fan with the same crap fan was silly. ...

I don't necessarily think that the modular OEM fans are crap. They are simple devices subject to extremely high temperatures plus all the wind and rain that makes it through the radiator every minute that your bike is in motion. That's a lot to ask. I do wish the bike had some smart circuitry to run the fan for a minute every time the bike was started or shut off.

The $80 fan motor is all that is necessary to replace to resolve a dead fan. The OEM fix is less complicated too since it does not require any customizing.

I suspect that your bike's previous owner may not have fully set the plastic blades onto the motor he replaced, hence the damaged radiator fins. I just replaced my fan motor and I know it took considerable force to push the blades back on to the motor, so much that I was worried about damaging the new motor. On a properly mounted assembly, the motor spindle should be flush with the front of the fan blade mount. Or maybe the two metal clips were on backwards which would create enough free play that the fan could touch the radiator fins.

How expensive was your Spal fan? Does it spin as fast as OEM?

I hope it works well for you.

[mjydrafter]

The Spal was ~$63 shipped with sales tax...  nothing really complicated or custom about it, other than the simple bracket.

The original fan motor is less than robust.  I was not impressed by the brush holders and the overall construction of the original fan.  The Spal impresses me in every way, including being waterproof.  Even if the Spal motor fails, the blades won't come forward drilling into the radiator.  The blade is held on with a circlip.

The PO gave me the old radiator that he replaced due to it leaking.  I suspect he didn't even remove the fan from the radiator (I did it last week, the screws were stuck pretty good).  I believe he got the current radiator with the fan and never tested the fan motor.  That fan blade had also drilled into the old radiator.  I had taken it apart to see if I had an extra fan I could use without buying a new one.

When I disassembled the current working radiator, the 2nd junk fan had, drilled a bit into this one as well.  It just hadn't gone into it far enough to cause a leak.

Even if my 2 fans and radiators are anecdotal, I've seen enough to know this modification is a less expensive, better alternative, than the OEM fan motor.

Obviously YMMV. :riding:

[Chaos]

thanks for the info.  Saved me the trouble of finding a good alternative fan.  The OE fan is one of the few weak points in old K's.

[mjydrafter]

I also made up a template for the bracket if anyone is interested.  I will have to scan it at work on Monday, and it will be bigger than a 8.5" x 11", probably need to be able to print 11x17 or legal size.

[Michael in AZ]

Add me to the template list, please. When time comes, I think I like your solution better than manual rewire (at least at my current skill level).

[Kyle10]

I also made up a template for the bracket if anyone is interested.  I will have to scan it at work on Monday, and it will be bigger than a 8.5" x 11", probably need to be able to print 11x17 or legal size.

Put me on that template list, as well please. Solid mod.

Thanks!

[mjydrafter]

I have scanned and attached a .pdf of the bracket I made up.  I will see about making a better one, since I am a drafter after all.  I will make up a new one as soon as I have a few free minutes.  This one will work for now.

I traced my bracket in pencil, and then had to go back over the pencil with a sharpie so it could be seen.  So, you may want to adjust it a bit. 

I thought about adding holes around the edge, but I don't think that the bracket will block too much airflow.

I had to scan it in on an 11x17 sheet, so if you print it without scaling it "should" be to scale.  I also added a CM mark and an inch mark so you can check it after you print it.

 :2thumbup:

*Edit to add: I got the fan here, no affiliation, just happy with them and their service.  Not to mention they are locals, so I even had to pay sales tax...http://www.universalpartsinc.com/HP_Parts.asp?CAT=SPAL%20FANS%20AND%20ACCESSORIES&SUB=6.5%20INCH%20ELECTRIC%20FANS

[Michael in AZ]

OK. Potentially dumb question. What gauge/thickness/type of metal did you use for your fabricated mount?  Looks like a great fix and is next on my list (the Herko fuel pump is chugging along like a champ!)

[mjydrafter]

Good question!  I will measure it at lunch for sure, but IIRC, it was 3/16"

It was a cut up Handicapped Parking place sign...  Now, look back at the pic with the cork gasket... :hehehe

And no, I didn't steal it. :neener:

 :yes

[Michael in AZ]

Any chance of a long-term report (now that you've been riding through the heat?). Any additional mods you would make in hindsight? Still debating this mod vs. replacement Bosch motor and a toggle. Having to get the mount fabricated puts them neck and neck $$$ wise in my case. Interested in what you've learned. Thanks.

[mjydrafter]

The fan is working fine, (I don't know that it's ever run in battle though) :dunno2:

I will test it one of these days, but I have no doubt it will work just fine.

I'm pretty sure the stock fans die from disuse just as much as anything.  Although, the melted brush holders seem to be a common theme.

[voodooskin]

+1 that the stock fans are crap, same radiator damage from the same "time to spool off the shaft and into something easily damaged"

My fan is JB Welded back onto the shaft, and the radiator is mended thanks to my local shop, but I think this upgrade is due this Winter once riding season ends and deferred maintenance season begins.  Thanks for the template and the documentation!

[Michael in AZ]

So I'm happy to report that I have completed MJYDrafter's mod pretty much step by step as outlined including using the bracket he drew up. I live in the Verde Valley of AZ. Surrounded by mountains on all sides. So lots of opportunities to overheat a fanless Brick.  Over this summer, there are several drives where the bike would just hit red light on heat. So after the mod yesterday, I spend 4 hours riding all the runs that would cause the bike to get hot. It was 101 hear yesterday. And muggy. So at the end of the day, my Legendary Flying Brick never got to red light. I thought I could feel a little extra heat on my legs once or twice, though. So at the end of the run, I parked and kept the bike running. That fan is deadly silent! Standing w/no helmet I could not tell for sure by sound if the fan was on. I put my gloved hand down by the engine, and let me tell you, that Spal can really push some air! Extremely happy with the mod. Plus just a little happy with myself for doing the swap without having to take the radiator off.  

Excellent excellent mod by MJYDrafter. I would like to suggest that it should be written up and submitted to the Lieberry. It really is that good a deal. Just my two bits.

[Roadbandit]

so 18 months later, I've bought a K75 and its lunched the fan. How unsurprising. Was about to write up about an alternative fan and lo behold… its been done.
A second hand fan over here is 175 clams. found the above unit on flea bay for 50 clams. It should be here by the end of the week.
Then I can go for a ride early new year and post some pics of the country around this way.

[enb54]

Well, after reading this thread, I'm taking mine apart to check it, then possibly trying one of the suggested fixes here. My bike has about 85,000 Km on it and likely needs this item to be addressed...

[Marky Boy OZ]

 :2thumbup:

Mate would have been a easier option...... Where were you ?????

[Roadbandit]

So I bought the same fan as appears in the first pictures in this thread.

I decided not to make a bracket to fit it up but rather take all the mounting tabs off with a flapper disc on an angle grinder.
I figured that the whole fan unit would go close to fitting inside the original shroud. Almost.
I removed the original motor mount and split one side of the BMW shroud to allow the new fan unit in.
Decided that things weren't quite lining up properly so split the other side after marking locations etc.
A small bead of silicone was run around the inside of the BMW shroud then the new fan unit pop riveted in place.
I also had to elongate the top hole about 4mm to account for a slightly stretched out shroud
The whole operation took about an hour…. not bad for a $50 fix as opposed to BMW wanting $400 for a new unit.

[mjydrafter]

^^^^^Hey, that's pretty clever! :clap:

[Boxer Metal]

Even easier, Google "Radiator Fan Zip Ties"

[Roadbandit]

my fan came with those zip ties and I did consider using them.
My concern is they'll damage the radiator in a short space of time so went the other way.
Keen to hear if others have used them and if there have been any issues over the long term

[mjydrafter]

I used some of those on a radiator fan in a Jeep.  I was not impressed with them. I think 2 of them broke.

[Roadbandit]

after just returning from a  2000km trip over the last few days, I can happily report the new thermofan does its job nicely.
Moves plenty of air. The bike had to cope with temps as high as 44deg… thats Celsius gentlemen or just over 110deg F in american speak.
It was a bit warm at times.

[F14CRAZY]

It sure beats sitting in traffic, 2-up, watching the VDO temperature gauge slowly go up past 240 degrees...(I was slow to replace my fan)