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charlie99

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well as started in another post here in the forum i have a restoration of our fuel level senders going on .

luckily on previous restorations the fuel level resistor - wiper has been in relatively good condition enabling me to just clean the rust off and resurface the resistance winding for a good operational result.

but i did acquire another unit via "frank the rat " from thom Hellbreakers ..(sp?) in holland , who offers  a lot of recycled parts .

this one was well and truly cactus . with just the mechanical parts seeming to be ...erm ...existing?

restoration of the fuel sender ...a work in progress so far  20210521

so on disassembly found the resistive windings actually corroded through in quite a few places .....bugga !!!!

restoration of the fuel sender ...a work in progress so far  20210522


ill step ahead here with the pic , having found a what seems to me a suitable resistance wire to replicate the winding , after a couple of attempts to buy the correct thing .
 it seems that 50 ohms per meter will suffice for the job , with just some simple calculations , available from a local (aussie) supplier ....

restoration of the fuel sender ...a work in progress so far  20230821

here it is , with now a sample of the nichrome wire i found that should be suitable across the windings . notice the frayed windings of the base backing  ...
restoration of the fuel sender ...a work in progress so far  20230816

just using my favorite nylon brush on the drill i was able to clean up the assembly , reasonably well .... with a rotary tool used to polish it up a bit more , but still leaving some traces of corrosion in there .

restoration of the fuel sender ...a work in progress so far  20230817

restoration of the fuel sender ...a work in progress so far  20230818


just arrived today i purchased a litre of "kbs Rust Blast ", which is supposed to cut the rust , etch the base material and leave a coating of zinc phosphate ...ready for electroplating some zinc back onto the surfaces . Well thats the plan going forward , possibly with a little nickle as well . unsure if i need to apply chromate after the zinc plating ...?

restoration of the fuel sender ...a work in progress so far  20230819

here's the result of the rust blaster ...looks as though it has done what it says ...win !!

restoration of the fuel sender ...a work in progress so far  20230820



so now considering the way to wind the coil across the base , keeping in mind the length needed to cover the wiper sweep ... i think ill have to find a .75 or .50 mm pitch bolt to lay down the windings with more or less equal turns


hopefully i have some bees wax on the way , as the windings are retained with something waxy ....and also to cover the electrical connections whilst in the electrolysis bath whilst plating happens ..
the journey continues

what do you think ...so far ?


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

moriarti

moriarti
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Bloody Marvellous, :1B:cant wait for next bit. restoration of the fuel sender ...a work in progress so far  112350


__________________________________________________
1984 k100 rs red/black VIN  0004449 Now sold to Olaf
    

Dai

Dai
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Nice one Charlie.


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

robmack

robmack
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Nice work.  Quite the task you've taken on.  As for winding the wire resistor unit, maybe a lathe with an adapter on the carriage that can guide the wire and maintain tension, and power the carriage with the lead screw for the given pitch.  Experiment with disposable wire first (like 30GA wire wrap wire).

http://k75retro.blogspot.ca/
    

charlie99

charlie99
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Thanks guys

Yes Rob thats the intertion to try with something relativly cheap as the nichrome wire is about $2 per metre  (34ga) i have in mind a small hand winder worth about $50  which looks to have a suitable gearset , ill gave to make a few arms for auto tensioning as the nichrome wants to run away from the bobin pretty quickly

Anyhow not impossible to do  

But i have a trip to plan end of the month so everything will be on hiatus till after then  tyres to buy etc 

Cheers


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

MartinW

MartinW
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Life time member
I have a question for Charlie and Rob. For Bricks not running a fuel gauge would it not be possible to do away with the windings and just have on and off for the low level light. I think that Bruce's K75s has stuffed windings but his low level light still functions due to dual wiper arms.
Regards Martin.


__________________________________________________
1992 K75s
    

robmack

robmack
Life time member
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Yes @Martin, that should be possible.  The wire-wound resistor plate is a separate circuit card from the one that detects low fuel level.  There are also two wiper arms - one for the resistor and one for the low fuel.  So, just remove the resistor circuit card and leave the low fuel circuit card in place and you have achieved your goal.  Make sure the upper wiper arm does not interfere with the operation of the sender.

http://k75retro.blogspot.ca/
    

MartinW

MartinW
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Thanks Rob you have confirmed my thinking. Most of the Bricks in the K Kronie Kluster don't have fuel gauges so repairs would be simplified. Maybe you could set up a organ donor scheme with non gauge owners donating their circuit cards.
Regards Martin.


__________________________________________________
1992 K75s
    

charlie99

charlie99
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as Rob says , no real issue 
but i have found many are unreliable 

but that could be because i have only ever been inside tanks that have extraordinarily high kilometers

anyhow this is what came off this sender 

it appears to be just single sided phenolic circuit board , etched for the desired operation , then tinned .

this one seems to have bent with the corrosion forming behind the "board " on the metal , evidence is seen with remains of rusty crap impregnated into the surface.

in any case it must have been fiddled with during its service life , with deep scores of the wiper into the surface , where a light sweep should have been calibrated (or is that just a hamfisted fix for someone that relies on the 4 litre lamp ?)

 restoration of the fuel sender ...a work in progress so far  20230822

restoration of the fuel sender ...a work in progress so far  20230823

its pretty much just held in place by a plasic rivet of sorts to the body of the mechanism

i guess ill have to cutout, etch and Tin a replacement to suit


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

MartinW

MartinW
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Charlie I've never seen one like that. Do you know it's origins as in model and year? scratch
Regards Martin.


__________________________________________________
1992 K75s
    

charlie99

charlie99
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martin all the ones i have seen look the same but that  gouge is deep

perhaps never seen it off the backing plate ?


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

MartinW

MartinW
Life time member
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Arrr the light illuminates the dim dark recesses of my mind. restoration of the fuel sender ...a work in progress so far  112350
Regards Martin.


__________________________________________________
1992 K75s
    

blaKey

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Hi guys and girls...it's been a while, but never-the-less, I still sneak a peek to see what's going on.

Charlie, I hope all is well with you. I was looking at a video of a bloke here in Oz bringing back to life a VB Commodore (V8 engine).

He was pulling apart the fuel tank and had a good shot of the original fuel gauge sender.

It looks remarkably like your busted K100 sender unit (the guts of it...not the tank mounting bit).

I could be wrong, I could be right (I should make that into a song!).

Google VB Commodore fuel sender and have a squiz.



Last edited by blaKey on Sat Sep 02, 2023 8:43 am; edited 1 time in total (Reason for editing : Clarification.)

    

charlie99

charlie99
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good to see you call in occasionally ol mate 

yes have played and sorted a few fuel senders , (with the local sports car club , getting things working again )

ill take a look ,, and thanks for the comments


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

warmshed

warmshed
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active member
I would fix the windings with a bit of epoxy adhesive at the sides, anything else may well dissolve in the fuel.

hope it all goes well.

    

CDNRider

CDNRider
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active member
Love this thread... I've just pulled the fuel sender from a k100 I bought on a whim this summer.

    

charlie99

charlie99
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well ive abandoned the rewiring of the resistor windings ....having found what seems to be an already manufactured part ...(likely out of china for this particular sample ) 

with the help of  Burkhard Förster...in another place , who had an injured wiper resistor assembly .
he pointed me towards a vw replacement sender .

which looks remarkably similar ... although i predict the differences in metal parts are a concoction of a copy of the original part , the original vw sender likely made in the same factory as the original bmw unit ....  seems likely .

anyhow the costs involved in getting a winder that would hold the board whilst i rewind it  the tensioning device for the really thin but resiliently straight wire and all that stuff , makes it a reasonable trade off to buy the part for under $25.00 (aussie) and mod it to fit .

some pics may help tell the story better ?

restoration of the fuel sender ...a work in progress so far  20230911

restoration of the fuel sender ...a work in progress so far  20230912

restoration of the fuel sender ...a work in progress so far  20230913

restoration of the fuel sender ...a work in progress so far  20230914

 the mod being to file back about 1/2 a millimeter across the board height , so that it fits into the locating jaws of the original assembly .

the resistance of the swept area is about the same as the bmw unit , although being speced at 10 to 90 ohms ...i measure about 107 ohms for this one .
so careful placement should give a good fuel gauge meter sweep of full to empty ..

one thing that is evident is that the sample here is not coated with a waxy compound like the bmw unit , im sure the waxy stuff would likely protect the windings from corrosion .. and hold them in place during operation ...
more research to be done ... 

you might notice that the oxidization of the base metal after  several weeks without carrying forward with electroplating ....yet 
...the rust blast stuff seems to work well .

 the journey continues


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

CDNRider

CDNRider
active member
active member
charlie99 wrote:he pointed me towards a vw replacement sender .
Assuming the replacement works out, could you point to a source, part number, or similar?

    

charlie99

charlie99
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Yes no problem   i have the part identifier

On the computer ....when i can get to it


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

CDNRider

CDNRider
active member
active member
charlie99 wrote:Yes no problem   i have the part identifier

On the computer ....when i can get to it
 No rush, and much appreciated.

    

CDNRider

CDNRider
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active member
charlie99 wrote:Yes no problem   i have the part identifier

On the computer ....when i can get to it

Any luck with the the part number and/or source?  Has it worked out as a replacement?

    

Ringfad

Ringfad
Life time member
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Check out VW part number 113919049D, I picked one of these copies of eBay for less than £14 but have not tried it yet.


__________________________________________________
restoration of the fuel sender ...a work in progress so far  Ir-log10

 ;BMW; K1 Black 1993 60K Km     ;BMW;  K1100RS Black 1996       ;BMW; K1 Blue 1990 25K Miles

 ;BMW; K1200RS Red
    

charlie99

charlie99
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Yes thats the one mate   they measure about 107 ohms and need a slight file to fit it in 
But looking to find some waxy substance that will hold the windings in place and protect the wire not ised for connection to the wiping arm...


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

MartinW

MartinW
Life time member
Life time member
Charlie I'm assuming that the waxy substance has to be fuel resistant. I have a waxy coating product that I'll try today to see if it's fuel resistant. It does take a while for the coating to dry so I might not have an answer today.
Regards Martin.


__________________________________________________
1992 K75s
    

charlie99

charlie99
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Yes would be interested to find out Martin

Was thinking of coating something and leaving it in e10 fuel for a couple of weeks
Cheers


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Have you considered using a fuel tank liner?  Fuel resistant and can be painted on. 

The stuff I use is RedCote fuel tank coating.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

charlie99

charlie99
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Point-Seven-five wrote:Have you considered using a fuel tank liner?  Fuel resistant and can be painted on. 

The stuff I use is RedCote fuel tank coating.
hmmm interesting concept 

thanks for the idea...

cheers


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

MartinW

MartinW
Life time member
Life time member
Sorry Charlie the stuff I tried didn't hold up on the fuel test. It was LPS 3 a waxy thick rust preventative coating that I had used previously. When I tried to remove it the only way I could remove it at the time was with thinners. It  however had been left drying for quite a few years. This time I let it dry for a couple of days and then sat it in a jar of fuel and the coating dissolved. You might want to try a fuel proof 2 pack epoxy.
Regards Martin.


__________________________________________________
1992 K75s
    

CDNRider

CDNRider
active member
active member
If the replacement part is also intended to be immersed in fuel (perhaps this an incorrect assumption?) why would you have to apply any kind of protective coating beyond what it already has?

    

Tranberg

Tranberg
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active member
CDNRider wrote:If the replacement part is also intended to be immersed in fuel (perhaps this an incorrect assumption?) why would you have to apply any kind of protective coating beyond what it already has?

The VW Beetle has the fuel sender mounted in the top of the tank, so it's not submerged in fuel, only exposed to fumes all the time.

The Chinese knock off is not engineered with durability in mind.

    

CDNRider

CDNRider
active member
active member
Tranberg wrote:
The Chinese knock off is not engineered with durability in mind.

Mine arrived this week, but with the Canadian winter just around the corner, I'm not likely to test it out before next spring.

    

Paddy1

Paddy1
Silver member
Silver member
would have not thought it possible to restore/salvage that piece. Brilliant.cheers


__________________________________________________
Riding Beemers since 1988
1986 K100RT, 1985 K100RS, 
2001 K1200LT, 2004 R1100S, 
2004 R1150, 1980 R65, 
2014 Zero FX, 2021 Zero SR/F
    

Tranberg

Tranberg
active member
active member
charlie99 wrote:Yes would be interested to find out Martin

Was thinking of coating something and leaving it in e10 fuel for a couple of weeks
Cheers
Why not the actual uncoated part for a few months or longer?

    

Tranberg

Tranberg
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My fuel sender looks worse than the worst pictured here, so are there any news in the matter?

    

charlie99

charlie99
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sorry no news just yet 

have something sitting in fuel as a test


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

36Back to top Go down   restoration of the fuel sender ...a work in progress so far  Empty New fuel sender Thu Dec 28, 2023 2:46 pm

CDNRider

CDNRider
active member
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Upon taking my old fuel sender apart, I saw that it was in terrible shape.  About the same time, I got notification that it's back in stock here: https://www.euromotoelectrics.com/product-p/flf-565edl.htm.  My new one should arrive next week.

    

CDNRider

CDNRider
active member
active member
restoration of the fuel sender ...a work in progress so far  Img_2110

    

Laitch

Laitch
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That looks like a Christmas cheese cracker on an easel. cheers


__________________________________________________
1995 K75 90,000 miles
    

Dai

Dai
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Life time member
Not even Charlie would touch that one.


__________________________________________________
1983 K100 naked upgraded to K100LT spec after spending time as an RS and an RT
1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

charlie99

charlie99
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Wow   and yuck ... restoration of the fuel sender ...a work in progress so far  177381


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
1987 k100rs ########   "Red"  - (red sports rs TWB style )
1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel , now sporting an rs main fairing )
    

yamaguzzi

yamaguzzi
Life time member
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That's pretty much what mine looked like.It went straight into the trash but I got lucky and found a good used one on Bay for 30 bucks .


__________________________________________________
1988 K 100RS ,1975 Moto Guzzi 850-T , 1971 BMW R60/5 , 1971 Yamaha R5B,1969 Yamaha DS6C ,1966 Yamaha YM1 , 1965 Yamaha YDS3
https://motoguzzi850t.blogspot.com/
    

CDNRider

CDNRider
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CDNRider wrote:Upon taking my old fuel sender apart, I saw that it was in terrible shape.  About the same time, I got notification that it's back in stock here: https://www.euromotoelectrics.com/product-p/flf-565edl.htm.  My new one should arrive next week.
 
Like a lot of you, I have many projects on the go, but I'm very pleased to be able to report progress with my '86 K100 project. I replaced
  • fuel sender, 
  • fuel pump, 
  • fuel filter, 
  • submersible fuel lines, 
  • exterior fuel lines, 
  • fuel injectors, 
  • front brake master cylinder, 
  • battery, 
  • and the fluids. 
  • And gave the gas tank a major cleaning.


Started like a charm!  Idles wonderfully! I can't wait to do some road tests, but the tires are from 2002, so I'll change those this week some time.

I find all of the plastic pretty clunky (although most isn't on, and I haven't seen it on) and the rectangular headlight screams 1980s.  I don't want to do a café conversion, but I'd like it to be stripped down somewhat. Any suggestions on minimal fairings (at a reasonable cost), ideally (but not necessarily) available from a North American source? Maybe sourced with a round LED headlight?

    

Two Wheels Better

Two Wheels Better
Moderator
Moderator
CDNRider wrote:Started like a charm!  Idles wonderfully! I can't wait to do some road tests, but the tires are from 2002, so I'll change those this week some time.

I find all of the plastic pretty clunky (although most isn't on, and I haven't seen it on) and the rectangular headlight screams 1980s.  I don't want to do a café conversion, but I'd like it to be stripped down somewhat. Any suggestions on minimal fairings (at a reasonable cost), ideally (but not necessarily) available from a North American source? Maybe sourced with a round LED headlight?
Lots of info on custom bikes with a search in the Forum's 'engine.' 
Perhaps in a new thread of your own that isn't specifically about fuel sender repair.


__________________________________________________
"How many cars did we pass today?" "ALL of them." ~J Tunstall
1977 R75/7-100, '93 K11/K12 Big Block, '93 K1100RS, '95 R100 Mystic, '96 K1100RS, 2 x '98 K1200RS, '06 K1200R & '09 K1300GT
    

glennpm

glennpm
Silver member
Silver member

Charlie99 regarding, "the resistance of the swept area is about the same as the bmw unit , although being speced at 10 to 90 ohms ...i measure about 107 ohms for this one, so careful placement should give a good fuel gauge meter sweep of full to empty .."


I'm interested in modifying a spare sender that I have. I took it apart yesterday and ordered a VW unit. How do you plan do this placement?
The BMW board and the picture of the VW one, really can't be adjusted side to side. With the higher resistance of 107Ω, the gauge will indicate empty too quickly

I've never cared for non-linear way my gauge reads. It will read full fine but the mid-range is inaccurate and then it quickly shows only a 1/4 tank.

Glenn

    

glennpm

glennpm
Silver member
Silver member
I'm thinking that wiring another resistor in parallel with the sender circuit board may be one solution.


Rt = 1/Rc + 1/Rn
We are after 90Ω at empty and not 107Ω
90 = 1/107 + 1/Rn or


Rn = 1/ (90-1/107) = 0.011 Ω which the new added in parallel resistor.


This is a very small value so I don't know where to get one .

Wrong formula, see post #49 below.



Last edited by glennpm on Thu Nov 21, 2024 10:50 am; edited 5 times in total (Reason for editing : Mistake in calc)

    

glennpm

glennpm
Silver member
Silver member
I'm thinking about using a piece of 26 gauge wire for the "resistor"

https://www.engineeringtoolbox.com/copper-wire-d_1429.html

AWG Gauge   (Ohms/1000 ft)
 26                 41.6

41.6/1000 = .011/X'

X' = .264' or 3.17"/8.05cm

    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
It's been a really long time and my brain isn't what it used to be, but I think the formula for resistors in parallel is:

Rp=(R1xR2)/(R1+R2)

If you use a 560 ohm resistor in parallel you will get a value of 89.835 ohms.

Hope this helps.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

glennpm

glennpm
Silver member
Silver member
Thanks, makes a lot more sense!

    

glennpm

glennpm
Silver member
Silver member
My post #45 was wrong for resistors in series. Below is the correction.


1/Rt = 1/Rc + 1/Rn
We are after 90Ω at empty and not 107Ω so Rt = 90Ω
1/90 = 1/107 + 1/Rn
1/90 - 1/107 = 1/ Rn
Rn * (1/90 - 1/107) = 1
Rn = 1 / (1/90 - 1/107)
Rn = 566Ω

This is where to solder in the parallel resistor, Rn.


restoration of the fuel sender ...a work in progress so far  New_re11

    

glennpm

glennpm
Silver member
Silver member
Rc varies by the sweep of the float pickup but Rn is a fixed value.
What is the impact across the linear sweep of the pickup?


1/Rt = 1/Rc + 1/Rn
1 = Rt * (1/Rc + 1/Rn)
Rt = 1 / (1/Rc + 1/Rn)


Ω
BMWVWRtvGauge Reading % Error
90.00
107.01
90.00
Empty
0%
87.50
93.64
80.34
 1/8
-7%
75.00
80.26
70.29
 1/4
-5%
62.50
66.89
59.82
 3/8
-3%
50.00
53.51
48.89
 1/2
-1%
37.50
40.14
37.48
 5/8
0%
25.00
26.76
25.55
 3/4
1%
12.50
13.39
13.08
 7/8
1%
0.00
0.01
0.01
Full
0%



Last edited by glennpm on Fri Nov 22, 2024 11:28 am; edited 3 times in total

    

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