Evening all, I know this subject has been covered before but could someone give a short answer ? I am about to put the K back on the road after 2 years in the shed. shes had a respray back to the original mystic red and a few bits and pices replaced. one of thease being the horns. but while im at it I was thinking of adding a fuel gauge. I have a a 1988 K100rt I have the standard two lights for low fuel but only one works. Can the sender run a fuel gauge and lights as well? or is it one ofr the other?

Cheers 

George

Two fuel lights? If the lights have a fuel pump symbol on the right-side one only, then the instrument cluster is correct because the left-side one is not connected up. IIRC the light comes on at about 11 litres remaining. The fuel tank should have the connector to the main wiring harness coming out of the rear of the tank. If these statements are correct, then fitting a fuel gauge is easy. There should be a green four-way connector under the tank about halfway along its length. This is the 'additional instruments' connector for the fuel and temperature gauges. If you have a standard RT fairing on the bike which has not been modded to take the extra instruments, remove the screen and the black wrap-around panel below it (not the flat panel that fits on top of the fairing - the one under that). Look on the back of the panel; you should find a 52mm circle molded into both sides. These are the mounting points for the fuel and temperature gauges and (obviously!) need cutting out.

You don't have to fit the temperature gauge. The OEM cable that connects to the green terminal block is a Y-cable so if you don't want the temperature gauge, just ignore the other connector.

The catch, coming up. Unless you are willing to mess with the in-tank fuel sender to reverse its output or, as Robmack has done, fit a signal inverter in the line, you have to use the OEM gauge. BMW in their wisdom inverted the signal output from the tank so that fully empty is maximum resistance. Guess what everybody else does.

Thanks Dai that sounds easy enough, I will check what connectors are there. The top of the fairing is now from an LT instead of the RT one but I'll find somewhere to mount the gauge....and put up with the reversed gauge for now.

Cheers 

Dai wrote:The catch, coming up. Unless you are willing to mess with the in-tank fuel sender to reverse its output or, as Robmack has done, fit a signal inverter in the line, you have to use the OEM gauge. BMW in their wisdom inverted the signal output from the tank so that fully empty is maximum resistance. Guess what everybody else does.

The reason for the reversed operation of the fuel sender is that virtually every other fuel level sender ever made is installed in the TOP of the fuel Tank.  Obviously, the conventional tanks on motorcycles can't really use this mounting configuration so BMW had to install the sender in the BOTTOM of the tank reversing it's operation.

LT fairing.... two choices on that. If it doesn't have speakers and a radio fitted, there's a 52mm molded circle on the back of where the speakers fit. Second choice is to find the LT additional instruments panel that bolts between the fairing and the windscreen. Unfortunately I can't find it on RealOEM.

GeorgeDaBikie wrote: Can the sender run a fuel gauge and lights as well? 

Yep.

Besides OEM, one of my bricks had a VDO fuel gauge that worked well.

Another option is to use the trip meter and try not to let the tank get much under quarter full.

Dai wrote:Second choice is to find the LT additional instruments panel that bolts between the fairing and the windscreen. I can't find it on RealOEM.

Is this it? realoem page.

No. That's the RT bit I'm talking about above.

Ah! Got it. This one:-

https://www.realoem.com/bmw/enUS/showparts?id=0536-USA-12-1992-89V2-BMW-K_1100_LT_0526,_0536_&diagId=62_0242

There's another possibility too, having just remembered that I checked this a while ago when fitting fuel and temperature gauges to LFB. The LT leg shields with the mountings for the extra gauges fit the RT lowers. It just doesn't look quite right because you get a big piece of exposed fairing... I ended up cutting holes in the top end of the RT leg shields.



I know my sig says that LFB is an '83 model and you can't fit fuel gauges to the early tanks. That's a late tank sitting on an adaptor that bolts to the early frame (no frame mods). The instrument panel is a late one (post '86) that's been clocked to read the same as the early instrument panel when I removed it. The wiring loom is one I made from scratch.

Hi  Dai  m not seeing a extra plug on my tank I think I might be  out of luck.


George

There's an intermediate aux gauge wiring harness that connects to this connector under the tank. The yellow wire comes from the fuel level sender.

There are also gauge pods that mount to RT/LT handlebars:

https://www.realoem.com/bmw/enUS/showparts?id=0516-USA-07_1986_K589_BMW_K_100_LT_87_0506,0516_&diagId=62_0239#62132303596

n/m. Sorry!

Hi Duck I can't find that plug. do you have a pic of where it would be on the bike? also the two blue plugs on mine are black.

If you have the tank off, it should be around halfway along the length of the top frame tube on the r/h side. Look for a white connector floating free with yellow, black, brown and green/black wires in it. It should be fairly close to the r/h handlebar switch connector. Yes; the anti-theft connectors can be blue, black or white. I have both black and white ones in the spares drawer.

Hi Dai, yep took a bit of digging around but I found it 

Dai wrote:



The catch, coming up. Unless you are willing to mess with the in-tank fuel sender to reverse its output or, as Robmack has done, fit a signal inverter in the line, you have to use the OEM gauge. BMW in their wisdom inverted the signal output from the tank so that fully empty is maximum resistance. Guess what everybody else does.

 Hi Dai, The Signal inverter that Robmack used, is it an off the self device or did he make himself?

Cheers 

George

GeorgeDaBikie wrote: The Signal inverter that Robmack used, is it an off the self device or did he make himself?

He used the existing card on the sender and flipped it. He explains the process in this post. Scroll down to the heading How to Modify the Fuel Sender to Make it Compatible with Modern Gauges.

Yeah - bookmarked that page years ago.

Lest it be forgotten, in post #6 daveyson indicates that a VDO gauge work with the Brick's wiring. Forum member duck has a webpage that supports the claim, so that alternative seems worth investigating if you can find the necessary gauge.

GeorgeDaBikie wrote:I have a a 1988 K100rt I have the standard two lights for low fuel but only one works.

That's normal for a1988 model. They originally had two lights, but the first light to come on was considered a nuisance to many, so it was deleted. The change was made during 1985. If your instrument cluster has litre marks for the two lights, it has been replaced and is not original.