BMW K bikes (Bricks)

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1Back to top Go down    Fuel Light not working on Tue May 15, 2018 2:44 am

George_Pap

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Hey all. My K100RT resurrection project reached a 75% of success. I m really happy, a bit more poor but happy Smile
Rode it for about 600km and it gets better and better. So far.
My challenge now is to get fuel lamp to lit.

The story
My bike had the early instrument with the 7 screws and the 7L + 4L lamps. It also has as you can guess the early fuel sender ( electronic stick )
When received the bike 7L and 4L were working properly.
Due to a short circuit that destroyed the green plug and the ribbon pcb bellow it I had to replace the instrument cluster though with an 1987 K75 one. The one with round pins and unfortunately only the 4L lamp.
By suggestions of great guys here i swapped the fuel sender pcb of the "new" instrument with the one of the old instrument. Since it was not working and due to replacement of the fuel pump and fittings i did purchased a used fuel sender from Motorworks and replaced that too.
Nada. Nothing.
I get no 4L warning.
Should i try to find an instrument with the 7L + 4L or there is a chance to make this one work?
Thank you


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K100RT (Early 1985 -nonABS)
    

2Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 3:54 am

Stan

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The low fuel sender on the early bikes...to about 1985 is the "stick"on the left side of the tank as you sit on it. The sender unit for the later bikes and also for the instruments with only the one warning light is on the right side of the tank and works in a different way. The later instruments low fuel light will not work on the pre 1985 bikes. Best idea is to use your trip meter to work out how far you can ride safely before you run out of fuel.


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1983 K100basic vin 0003960 colour red
1987 K100RT vin 0094685 colour, orange peel, sorry, pearl
    

3Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 4:10 am

George_Pap

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@Stan wrote:The low fuel sender on the early bikes...to about 1985 is the "stick"on the left side of the tank as you sit on it. The sender unit for the later bikes and also for the instruments with only the one warning light is on the right side of the tank and works in a different way. The later instruments low fuel light will not work on the pre 1985 bikes. Best idea is to use your trip meter to work out how far you can ride safely before you run out of fuel.

This is what i doing Stan for the time. But afte a couple of weeks riding i felt that the fuel consumption is inconsistent based on the tripmeter. Already run out of fuel a couple of times due to this. Sometimes i get 100km out of 6lt of fuel, sometimes i get 80, thats why i feel the need of a warning lamp.
So as i can understand you say that the early fuel sender of my bike is not going to trigger the 4L warning fuel lamp of my newer instrument cluster even that i have already replaced the pcb board with the old one. Correct?


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K100RT (Early 1985 -nonABS)
    

4Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 4:33 am

MartinW

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Fill up based on your worst fuel consumption which according to you is 80 Km. Fill the bike up after you have done 70 km after the fuel light has come on, or sooner depending on fuel availability. It is not wise to run your bike down to empty. As soon as my fuel light 7 litres left comes on, I will fill up at the next available Service Station. I've never run out in twenty years of owning the bike.
Regards Martin.


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K75s Hybrid
    

5Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 6:52 am

George_Pap

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@MartinW wrote:Fill the bike up after you have done 70 km after the fuel light has come on, or sooner depending on fuel availability.
Problem here is i dont have a working fuel light Martin Sad


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K100RT (Early 1985 -nonABS)
    

6Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 7:47 am

Dai

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As Stan says, your current setup is not going to work. You need an early 4L/7L instrument panel. It's possible to get the later one to work with the earlier sender by modifying the main PCB but having done it, it's fiddly and I'm not sure it's worth the effort. I'm an inveterate fiddler (shame the emoticon is missing... Twisted Evil )


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'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

7Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 9:46 am

RicK G

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My fuel gauge is a trip meter and experience. Pushing a bike is a real PITA.


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"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats." from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

8Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 9:54 am

George_Pap

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@Dai wrote: to get the later one to work with the earlier sender by modifying the main PCB but having done it [smiley]https://illiweb.com/fa/i/smiles/icon_twisted.gif[/smiley] )

Dai swapping the new instrument's PCB with the new instrument's PCB board isn't enough to get it working? Of course some pins of old PCB are on the air since there are no corresponding female plugs on the new one.
Could please let me know of the full modification needed? I m not the most delicate electronic guy but.. maybe worth a try Smile

Sent from Topic'it App


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K100RT (Early 1985 -nonABS)
    

9Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 9:55 am

George_Pap

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This is the PCB board I swapped.

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K100RT (Early 1985 -nonABS)
    

10Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 9:57 am

George_Pap

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@RicK G wrote:My fuel gauge is a trip meter and experience. Pushing a bike is a real PITA.

You bet it is Rick!! I m still trying to estimate my fuel consumption though.
I have even made a thought to carry a spare fuel canister on the rear case until nailing the real l/100km value.

Sent from Topic'it App


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K100RT (Early 1985 -nonABS)
    

11Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 1:43 pm

Dai

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George - I'm very reluctant to start trying to write up the changes I made as it means destroying another main PCB to get the required pins to start modifying the later one back to earlier standards. I happened to have a defective main PCB lying around, so it was a case of nothing to lose.


__________________________________________________
'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

12Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 1:51 pm

George_Pap

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I see. But...
Don't forget that I already have a semi destroyed instrument cluster lying around Smile the one that was on the bike initially .

Sent from Topic'it App


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K100RT (Early 1985 -nonABS)
    

13Back to top Go down    Re: Fuel Light not working on Tue May 15, 2018 10:51 pm

Laitch

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@Dai wrote:I'm an inveterate fiddler (shame the emoticon is missing... Twisted Evil )
scratch



Last edited by Laitch on Wed May 16, 2018 1:43 pm; edited 1 time in total


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1995 K75T 68,000 miles
    

14Back to top Go down    Re: Fuel Light not working on Wed May 16, 2018 4:07 am

Stan

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There is always plan B. A sure way of finding out how much fuel you have is to use a method that costs nothing and every bike, pre 85 and younger is covered. You use a digital fuel gauge......open tank, stick your digit in, feel how much fuel you have, close cap. Do not lick your finger......unless you like it.
drunken Laughing


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1983 K100basic vin 0003960 colour red
1987 K100RT vin 0094685 colour, orange peel, sorry, pearl
    

15Back to top Go down    Re: Fuel Light not working on Wed May 16, 2018 7:33 am

George_Pap

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@Stan wrote:There is always plan B. A sure way of finding out how much fuel you have is to use a method that costs nothing and every bike, pre 85 and younger is covered. You use a digital fuel gauge......open tank, stick your digit in, feel how much fuel you have, close cap. Do not lick your finger......unless you like it.
drunken Laughing
lol! lol! lol!

The old fashioned way Smile


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K100RT (Early 1985 -nonABS)
    

16Back to top Go down    Re: Fuel Light not working on Wed May 16, 2018 7:43 am

Dai

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@George_Pap wrote:I see. But...
Don't forget that I already have a semi destroyed instrument cluster lying around Smile the one that was on the bike initially .

Sent from Topic'it App
If the main PCB is still intact, swap that over.


__________________________________________________
'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

17Back to top Go down    Re: Fuel Light not working on Wed May 16, 2018 7:49 am

George_Pap

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By main PCB you mean the hard plastic PCB board or the blue film cable ?
Or both?

Sent from Topic'it App


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K100RT (Early 1985 -nonABS)
    

18Back to top Go down    Re: Fuel Light not working on Wed May 16, 2018 1:31 pm

Dai

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Ignore me - that was a really stupid reply Embarassed . I should have remembered that your original main PCB is literally toast. I just got an LT instrument panel off ebay because

a. my speedo is playing stupid again
b. it was cheap Smile

So I'll be converting that in the near future. I'll post a 'how-to' but it will come with lots of caveats because it's way to easy to destroy the blue film PCB with the soldering iron.


__________________________________________________
'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

19Back to top Go down    Re: Fuel Light not working on Wed May 16, 2018 1:41 pm

George_Pap

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@Dai wrote:your original main PCB is literally toast.
yup. totally toast it is!
Anyway. i'll keep my eyes on for an early '85 instrument on ebay. Till then i ll keep the lady top refuelled every 100kms to be sure.


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K100RT (Early 1985 -nonABS)
    

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