K100 16V Running Rich?

[mitcher9]

I hope this note helps some folks out there if they have a problem with their 16V bike running rich.

I bought my K100 16V to replace an older 8V bike a year or so ago. The first thing I noticed was that the fuel consumption was high (low 30s per gallon) although the bike started and seemed to run well. The engine temperature gauge indicated low (just off the blue segment) and the plugs were quite sooty with dry carbon and on opening the throttle quickly a puff of grey smoke cam out of the exhaust. All the signs of a rich mixture.
Following all the advice on the forum, I checked the thermostat, air temp, water temp, air pressure senders, mixture rheostat, throttle position sensor and probably a number of other components over the best part of a year but no matter what I did the bike ran rich.
One of the first things I did was to get the Motronic unit to give me the fault codes using the advice on the forum but I could not get the temperature warning light to come on. I therefore used an analogue voltmeter to "read the codes" but no fault coed was ever logged.

After a period of resigning myself to a rich running bike and believing that's why the previous owner sold it, I investigated the temperature warning lamp to find that simply the bulb had failed. On replacing the bulb I immediately noticed that the bulb came on with the ignition and went off as soon as the engine started!

The bike was transformed into a lean running machine with nearly white plugs. Mixture was now too lean due to me excessive fiddling with the mixture rheostat! That was easily fixed. The engine warms up quickly and the temperature gauge is now in the middle of its range.
In conclusion, the temperature warning light function is checked by the Motronic unit on ignition switch on. If the Motronic cannot get the lamp to light it must switch into a fail safe mode by chucking lots of fuel into the engine to keep it cool and ignores all the other sensors!
So, if your 16V K bike starts to run rich, please check that the temperature warning lamp is working before tearing your hair out.
 :clap:

[YoungEngineer]

Thank you for this information. I have had exactly the same issue. No amount of fiddling could reduce fuel usage. Computer was unable to read out any codes when pin one grounded.


 The difference with my setup is that the light is functional however only visable when diagnostics pin 1 plug grounded.


it would not turn on with the rest of the idiot lights when ignition was turned on. My theory is that it has something to do with my abs module being removed.


As you mentioned the computer defaults to a stinking rich safe map.


Can anyone else confirm that they have removed their abs computer and still retain the temp warning lamp function on startup?

[The Mighty Gryphon]

Wow!  I removed the ABS from my K100RS4V when I did a restoration on it and then had a rich mixture that sooted up the plugs.  While they were very black, mileage was in the 40's and the engine ran okay. 

To get the plug readings right I bought an exhaust gas analyzer and reset the CO pot to get 1.5% CO.  Bike runs better, but plugs still look a little sooty, but still better than before.

I can't say if the ABS removal was the cause of the rich mixture because at the same time I replaced the idiot lights with LED's.  I know that LED's interfere with some of the stuff on the bike.  I had to reinstall the bulb in the alternator warning lamp because the LED didn't excite the alternator properly.  I wonder if the LED in the temperature warning lamp also causes a problem.

[YoungEngineer]

My temp warning lamp is a normal bulb as far as i am aware. This can only point to the abs computer being somehow linked to the motronic or instruments and part of the self check. It would be good if someone could confirm.


Btw I'm not sure if the temp warning light comes on during power on for the K100 I thought it was only a k1100 thing

[The Mighty Gryphon]

My K100 is a 4 valve model with Motronic. I think it has a lot of the same operating logic as the 1100's.

[YoungEngineer]

Does your temp light come on with the other lights before startup?

[Filmcamera]

Mine does yes - I do have ABS but as an experiment I unplugged the ABS brain and the temp light still comes on when I turn the ignition on.

[YoungEngineer]

That's very helpful information filmcamera. That tells me that my problem is with my computer or elsewhere. Dammit

[The Mighty Gryphon]

I have removed the ABS from my bike(Filmcamera has it on his now) and yes, the temperature idiot light comes on along with the oil pressure and alternator lights when the ignition is turned on.

I haven't looked at the wiring diagrams of our bikes to confirm it, but have you checked the Temperature Relay?  If I am not mistaken it has an output that goes to the Motronic unit.

[YoungEngineer]

The K1100 1994 does have a temp relay but looking at the wiring diagrams it does not have any connection to the temp light. Only one input from the computer and one to the fan. It is the computer which controls the relays operation and not the temp/fan control box like earlier K bikes. Infact the temp sensor only shares info with the computer so I am almost sure that if you disconnect your motronic you will find that the temp light will no longer illuminate

[bitcoinbot]

Hello guys< I have the same issue about one year as I turned my K1100 RS 1995 to a cafe racer.
Can someone show that wiring in wire diagram?

[bitcoinbot]

Nothing special...
I removed all wires and made wires from the scratch with motogadget m-unite v.2 and m-button

[Laitch]

 Your moto is having the "same issue". Describe the issue, because I'm reading about a couple of issues here.

[bitcoinbot]

I couldn't find in my profile can I add that info.
It's BMW K1100 RS 1995 year
The issue is rich fuel mixture and it's smokes also wasting oil. I already checked engine and it's perfect condition.

[Laitch]

An engine is not in "perfect condition" if it smokes from over-fueling and excessively uses oil. There are more diagrams in our Electrical Diagrams/Schematic section for 1994 and newer K1100 models. Describe the symptoms exactly and whether you have checked the crankcase breather hose condition, checked for correct valve clearances, and balanced the throttle bodies.

[bitcoinbot]

I understand please read the topic post from mitcher9
Soon will make a video.
Do you have that diagrim which you mantioned?

[Laitch]

I understand please read the topic post from mitcher9
Soon will make a video.
Do you have that diagrim which you mantioned?

You should get familiar with a site before you start using it. On the Home page menu, you will see a section heading Electrical Diagrams~Schematics. Click on it, find your model number, download the diagrams. It is a 7-page pdf.

I read the post from mitcher9. The problem here, bcb, is his solution involved the original instrument cluster. You don't have one. You have an aftermarket instrument which you have wired into the system.

[Laitch]

How did your wiring procedure differ from the one in this video?

[bitcoinbot]

Hey I know this guys, yes the wiring the same but I did more cleare.
The issue is with the temperature warning light function is checked by the Motronic unit on ignition switch on. If the Motronic cannot get the lamp to light it must switch into a fail safe mode by chucking lots of fuel into the engine to keep it cool and ignores all the other sensors!

[johnny]

greetings...

how does it know when the light is lit... does it use a photocell...

j o

[Laitch]

Hey I know this guys, yes the wiring the same but I did more cleare.
The issue is with the temperature warning light function is checked by the Motronic unit on ignition switch on. If the Motronic cannot get the lamp to light it must switch into a fail safe mode by chucking lots of fuel into the engine to keep it cool and ignores all the other sensors!

We don't know if you have wired your instrument correctly, but it seems to me—if your understanding is accurate—that your task might be to connect the Motronic to a dedicated warning light circuit rather than a multi-function light circuit. Stuntex make it look easy, don't they? Have you communicated with them?

[bitcoinbot]

Yes I'm in touch with them. Motogadget only controls light, turners signals etc. not Motronic. It just tune on power for Motronic that's it.
Here's a video

[johnny]

greetings...

thank you for poasting the video...

my brick smokes more than that and my hawt light illuminates...

i putts my gas and oil expenses on a credit card... the more i spend the bigger my rebate so all is good...

j o

[bitcoinbot]

Thank you
It shouldn't smoke, what about gas and oil expenses?

[Laitch]

Thank you
It shouldn't smoke, what about gas and oil expenses?

An over-fueling engine , excess fuel will rinse oil from cylinder walls. That will lessen compression and affect mileage. An air intake system with clogged crankcase ventilation will consume oil.