My fairing mounted fuel gauge (not the warning light in the instrument block) shows only 3/4 full when the tanks up to the brim, and then shows empty when there's a 1/4 tank left.

Is the gauge dicky, or could it be a sensor in the tank thats at fault?

Any ideas folks?

Could be that your connectors are dirty. This will cause the gauge to register a higher resistance than usual and a relative reduced resistance change between full and empty. Clean all the electrical connectors between the tank float and the gauge and let us know the result?

Thanks ReneZ

Will do.

The other pair of pins in that same plug carries the fuel pump power and that going open circuit just as you drop a gear and go Wide Open Throttle to pass a big truck is a BAD THING!

Really worth checking the connector for good connection and giving it the full Deoxit treatment and do not use the oft touted dielectric grease on the pins that is an insulator and although it excludes oxygen and moisture it does not help with conductivity whereas Deoxit does.

In my opinion the only place for that grease is for excluding water entry in the backs of plugs and in spark plug caps I strongly believe it has no place in low voltage connector sockets and pins nor on fuses, earth grounds, battery terminals etc. I also feel the same about WD 40 or any other lubricant on switches, sure lubricate the mechanism sparingly but the contacts need treatment with Deoxit. As they say YMMV
Regards,
K-BIKE

Bonzo wrote:My fairing mounted fuel gauge (not the warning light in the instrument block) shows only 3/4 full when the tanks up to the brim, and then shows empty when there's a 1/4 tank left.

Is the gauge dicky, or could it be a sensor in the tank thats at fault?

Any ideas folks?

Your error is constant (3/4 on the gauge reflects a full tank and empty on the gauge reflects a 1/4 tank)
It seems that the rod activating the gauge is bent to high by the equivalent of a 1/4 of a tank
I personally think that it is nothing wrong with the electrical, but there is an adjustment problem. I would simply bend the rod to reflect the real level of fuel in the tank (bending the arm down by the equivalent of 1/4 of a tank).
Does it makes sense???

Doh,
Failed to read the original properly, I am sure is Bert is spot on, my guess is someone refuelling the bike snagged the float arm with the petrol nozzle and put a permanent bend in as Bert diagnosed. Previous comment about the importance of good connections still applies just not as a cure for this problem.
Regards,
K-BIKE

Sorry team, don't agree. If an empty tank is indicated with 1/4 full than a full tank should be 1 1/4 full, nor 3/4, if we think the arm is bent (or it should indicate full for the first 1/4 of the tank. Or it is electrical or something snags the arm/float that does not allow movement outwith of the indicated range. Regards, Rene.

Rene,

I re-phrase the first post from Bonzo:
You have 5 liters in the tank and the gauge indicates 0
You add 15 liters and the gauge indicates 15 liters (or 3/4) but in fact you have 20 liters in the tank (5 +15).
The rod must have been bent upward and the 20 liters electrical contact is already ON with a level of only 15 liters of gas. The float should be traveling another 1/4, but is locked by the top connection in the switch. This means that the float is immersed and not floating from 3/4 to 4/4 fuel level.
Now, when the fuel level is down to 1/4, the "0 liters" electrical contact is ON preventing the float to lower itself any further. From a fuel level of 1/4 to 0 the float is not touching the gas and if floating in the air.

If you bend the rod and float by 5 liters downward and it will indicates the right value.

This is the nice thing about a forum, everybody has its opinion and we all debate about the solution.
The constant error caught my attention otherwise, yes like everybody I would have given advices on the electrical connection.


Bert

Bert, always happy to learn, but am wondering.

If " the 20 liters electrical contact is already ON with a level of only 15 liters of gas" is the case, the dial should indicate full instead of 3/4, right?
He seems to indicate it is the other way around; a full tank shows 3/4 on the dail, so the arm doesn't reach max position.

I appreciate it can be a bent arm/rod/lever, but it seems to indicate 1/4 tank less on the dail than actually there. Then the float would have been bent up and I don't see that easily happen. However, love to be proven wrong; I learn and the problem gets solved.

Cheers, Rene

ReneZ wrote:Bert, always happy to learn, but am wondering.

If " the 20 liters electrical contact is already ON with a level of only 15 liters of gas" is the case, the dial should indicate full instead of 3/4, right?
He seems to indicate it is the other way around; a full tank shows 3/4 on the dail, so the arm doesn't reach max position.

I appreciate it can be a bent arm/rod/lever, but it seems to indicate 1/4 tank less on the dail than actually there. Then the float would have been bent up and I don't see that easily happen. However, love to be proven wrong; I learn and the problem gets solved.

Cheers, Rene

Good point Rene!
This was originally a simple question but I got confused.
In general, a electrical fuel gauge is no more than a voltmeter and the gauge is a variable resistance.
Do the fuel level light(s) are working correctly? On the early models you have 2 lights (4 liters and 7 liters).
If they work correctly, I would say the electrical dial display is bad or It could be simple as a corroded connection.

Bert

I think that they changed from the two lights version to the one light (5 ltrs) at the same time they created the possibility with the loom to connect the additional instruments option to include the fuel dial.

Back to Bonzo's problem. I understand that a full tank is indicated with a 12 Volt signal and the reduced voltage resulting a lower tank level makes the dial go down.
Bert, I agree, it could be a bent float arm, but would also consider corroded connections. These would increase the resistance and lower the resulting signal voltage at the dial.

Interesting one! Cheers, Rene

Sorry for opening up a can of worms folks :-)

I ran the bike (almost) dry this weekend to a). change the fuel filter, and b). see if the red warning lights came on. (My old K-RS's didnt have the extra fairing gauges, and I wasnt sure if the newer models did away with the lights and just used the fairing gauges).

No lights came on on the instrument cluster :-(