BMW 92' K75S - A "Flying Brick"

Did some more wrenching the other night. I had the whole front end torn apart. I am trying to tackle the overheating problem, and I believe I found the source. It looks like my radiator fan motor is no longer working :'(

I followed this guys testing instructions: http://www.ibmwr.org/ktech/fan-diagnosis.shtml
Temperature Probe: ok
Temperature light: ok
Radiator fan: Didnt get any resistance through the leads on the fan motor, and didn't get it to run when I jumpered it. Ill do another round of testing before ordering the motor, but so far that is my main suspect.

After that I took off the front end to paint the front rim and install the fork boots. They both turned out nicely
I also removed the gas tank flap. It gives you about another 1/2 gal in capacity

Here is what I still have to do:

Brake System Flush
Replace Fuel Pump Boot - in the mail
Clean Fuel Injectors - used some SeaFoam
Replace Taillight Bulb - trying to find a place on town that carries this
Replace Fuel Lines - picked some up today on the way home
Troubleshoot Cooling Fan
Replace Vacuum Port Caps and Hose
Patch leaks in fuel tank


Pics below:





The electronics tray looked brand new inside. Nice and clean


Relay was also nice and clean. No corrosion


Gas tank flap removed


Getting all cleaned up


Man I need a real bike stand. BADLY


Rear wheel


All wrapped up except for the belly pan.

Progress!!!!

Tonight I dug back into the bike. I replaced all the dried out and cracked fuel lines (made sure to use high pressure lines SAEj30R9 rated) as well as relocated the fuel pressure regulator. Also replaced the vacuum port caps and the vacuum line from the throttle bodies to the fuel pressure regulator.

Under the airbox I found all sort of crap and dirt. This is where the FPR used to live. (its the brass cylinder with three hoses going into it) Behind the throttle bodies.


I followed this guys idea for the relocation: http://k100rt.aforumfree.com/t2837-fuel-pressure-reg-relocation-now-with-fuel-cooler-added

I am very happy with it. I just have to replace the simpson strong tie (hahaha its all I could find) with a piece of aluminum.

Here is its new home with most of the new fuel lines attached. Outside of the throttle bodies


Much easier to access for maintenance if necessary and all the fuel lines are one place now. The fuel tank should stay a bit cooler now as all the fuel lines are on the outside of the bike and not run right above the motor.

The bike runs much smoother it seems. I am sure I had mad leaks in the cracked vacuum caps and old cracked vacuum line

If you haven't ordered a new fan motor - check this out.

They have a habit of seizing through non-use. In cooler climates they barely come on - ever ! Most cases can be solved with lots of WD40 / similar and revolving the spindle by hand. Then check the wiring / any fuses involved. I've brought 3 motors back to life this way !

While you've got the seat / tank off - check and clean ALL wiring connectors. Take the connectors off the back of the instrument binnacle - and again clean / lube. You may well find the insides are green with corrosion . Bad connectors [ through dirt / corrosion ] are the biggest single source of poor running on Kays. The other source of aggravation is the fuel pump / filter. definitely worth changing the filter and while you're at it check the condition of the internal [ tank ] connections.

Wealth warning .........Kays are addictive ! 8)

Haha. They are so addictive.

Thanks for all the info. I planned on doing all those thing before ordering a fan motor. I actually bought some contact cleaner and dielectric grease last night for that purpose.

I did reach in and spin the fan. It seems to spin freely. Should I take it off and go through everything on it like you said? Are there more connections than just the one two prong connection going to the motor? I think its brown and purple/white

My fuel pump boot should be here any day, so thats next on the list. The old one is a little to "soft" for my liking, I figured better same than sorry. Ill throw on a new fuel filter when I do that too. And probably repair the leaky tank as well.

Thanks for all the help. I am still learning this bike

Looking good man, you're making fast progress. I just replaced the regulator and lines on my bike this last weekend but didn't know about the relocation tip, I'll have to look into that. I still haven't heard back from that guy about the parts either.

Cool,

Do the regulators actually go bad on these? Or do they just get clogged?

Not sure, I didn't even check to see if it worked. As bad as the rest of the fuel system was I just figured I might as well replace it too.

IF the motor spins freely, it might well be the sender at fault - short the motor out directly across a battery to determine if it is working or not. Generally - if they are spinning freely - they're OK [ not always! ]

There is a sensor [ temp ] which affects the fueling of the system. In your first pic [ before relocation ] there is an alloy take off [ front left of block ] there is a temp sensor screwed in the side of the housing here. Check it for operation, and again - keep a spare - it WILL go awol at some stage in your ownership !

So a couple days ago I tackled the fuel tank problems (leaks + fuel pump boot)

I have never seen so much crap inside of a tank. This thing was seriously dirtier than my cb350's tank. Luckily the tank itself being aluminum was is good shape, but there was about 2 TBSP of crap inside the tank. I have no idea what it was.
All that dirt and dust was inside the tank as well as chunks of who knows what.
Old boot and filter


The old boot was pretty much shot. It was starting to get pretty mushy


Also the filter on the bottom of the pump was also in bad shape. It was still intact but I accidentally torn it while removing. Oh well it wouldn't hurt to replace it, but now I am stuck waiting for it to arrive (had to order it)


Next I tackled the leaks. They were down in the most common area, at the weld seams, water from inside the tank eats at the welds and eventually corrodes them enough to where they leak. I scraped them out with a razor and roughed them up with some sandpaper before applying QuickSteel. A super handy epoxy putty. When is hardens you smooth them out with sandpaper



I also got bored and hacked my old MASSIVE windshield up with and angle grinder. HAHAH ;D.
I trimmed it down to much closer to the stock size. Not as good wind protection, but looks 10x better in my opinion.



I also cleaned (with electrical contact cleaner and dielectric grease) every electrical connection I could find with the tank off.
I still have to tackle the radiator fan issue. Maybe Ill go do that now as I have some time...

Radiator fan problem found.

Good news is I found the problem, better news is the fan motor is still good. Bad news is that that actual magnetic slides that touch the copper cylinder is where the problem was.

Sorry for my poor description I am pretty bad with even simple electronics. Pics may explain better

Bike torn apart for radiator fan motor surgery. Front fairing and radiator removed.


Fan and motor pulled off.


Here is where is did a bunch of looking, thinking, and testing. Per Beachcomber's instructions (thanks) I went straight from the battery to the motor harness. Nothing...Straight to the motor harness after the wires, nothing...

Next I began closely inspecting the harness and motor itself. Basically there is a copper cylinder in the center of the motor and two magnetic sliders that touch it. ( 1 hot and 1 ground). Well the ground slider was nice and lined up, but upon close inspection the hot slider was barely touching the copper cylinder and was all crooked and the housing looked melted.

Next I pulled it off and that was indeed the problem. I touch my leads from the battery directly to the copper cylinder and the motor spun to life....

The good side - noticed the silver clip and how centered the small copper coil and housing are


The bad side - no silver clip, I have no idea how that disappeared and how crooked and melted the housing is


My theory is that silver clip that holds the small copper wire and housing centered "disappeared" and as a result the hot lead touch the actual motor housing causing it to short and melt. This also probably blew the fuse, but that was replaced and no one ever thought otherwise.

Now if I can just track down the actual wiring harness part of the fan motor that would be excellent.
This is what I need. Just the harness. Not the whole motor


Actually, this is all I need. Just this one little dang piece. From the brown wire to the copper coil and plastic housing.


Will I be able to find just that...Probably not. I would rather not have to spend $70 and get the whole fan assembly

Well tracked down ! Just logic really - I'm also crap with electrics, but have a design engineers' mind.

I'm certain you would be able to find the part - try the K11OG forum [ US ], good bunch of guys - tell them Beachcomber sent you ! [www.K11OG.com. ?? ].

I'll check out my old stock when I go down to the workshop in the next couple of weeks and see if I have got the harness part.

Cool,
I'll hop on there and check. I think I'll also email beemerboneyard and see what he has. Thanks for all your help beachcomber

Well an update finally...
I have been doing a bit of research trying to track down possibilities for my radiator fan motor repair/replacement.

I opted to go with replacement, as I had no luck tracking down the actual harness. Will help from the gents on Motobrick and K100 Forum I decided to replace the existing motor and fan with a newer 6.5" Spal Puller fan. $50 shipped from:
http://www.brightonracingproducts.com/65-Spal-Puller-Fan-20-002.htm

The 7.5" will fit aslo, but takes a bit more finagling.

Ill just have to fad a few small mounting brackets and the 6.5" should fit nicely. Should be here in a couple days. Ill update shortly.

Also got some new fuel line for my fuel filter -> fuel pump. Submersible fuel line is $$$ it cost $28 from Napa for a foot
Still need to track down some 1/4" submersible line for the return hose inside the tank

I ordered most of my fuel tank parts from A&S BMW parts, they weren't cheap though.

http://www.ascycles.com/Illustrated_catalog2/MicroList.aspx?id=51745&catID=16&catname=Fuel_Supply

Yeah,
I may have to do this for that last length of line. Somewhere has to sell that stuff other than the dealer. I was told to check out a boating place, so I called one today. The guy I talked too was not confident his could be submersible.

Maybe a lawnmower place? There is a small fuel filter inside most gas tanks on a mower.

Ill call them tomorrow. Hopefully my fan will arrive before the weekend. I cant wait to get back on this thing.

p.s. thanks for the info

Great read .... good to be in the Klub

Hey man I just got my k75 project bike running this weekend and I wanted to see what oil filter wrench you used. I bought one from Kragen but it was too big and didn't fit through the hole in the sump. I ended up pulling the sump plate off to change it which also gave me a chance to see if there was anything scary looking floating around in there. Needless to say I'd rather not pull the sump plate everytime I do a oil change. I still need to flush out and bleed the front brakes but I took it for a short ride and it seems like it's going to be a fun bike. I might have some of that in tank fuel line leftover too if you haven't found some yet.