Fuel level not accurate at speed???

[Smellii]

If I'm running at highway speed my fuel level always reads empty or nearly empty. Kinda defeats the purpose of the feature when traveling. I was wondering if this is normal. If not what could cause this? Thanks.

[RHODESIA SMITH]

My 850 does exactly the same thing. it is annoying hey?
What I tried to do , but it did not work so I took it out is to put a 220ohm resistor in parralle with the gauge. It did seem to make the needle on the gauge less prone to drop down, but then it did over read. I have since removed the resistor.

The only other way is to try and make the float less loose in its hinge? dont know how this could be done.

any Ideas any one else?

[MisterOh]

Yeah that fuel gauge is annoyingly inaccurate haha. Engine braking will cause mine to display that I have twice as much fuel left.

[DanTheMan]

The trip odometer and stop lights are the best gauge. If you've got, say, 98-120 miles since your last fill-up on your 850G, and you haven't been doing too much full throttle operation, you've probably got about a 1/4 tank left and should be looking for a place to fuel up. If you're on an 850L prior to the '82 model, you're probably sitting on the side of the road waiting for someone with a gas can or siphon hose to help you out...

[Smellii]

Thanks guys. I'm going to look into the float idea a little bit more, see if it's worth starting another project.

[1948man]

Have you seen the tutorial here http://members.dslextreme.com/users/bikecliff/ on the right hand column. It might not cover that exact problem but will provide some basic info.

[Steve]

The trip odometer and stop lights are the best gauge. If you've got, say, 98-120 miles since your last fill-up on your 850G, and you haven't been doing too much full throttle operation, you've probably got about a 1/4 tank left and should be looking for a place to fuel up. If you're on an 850L prior to the '82 model, you're probably sitting on the side of the road waiting for someone with a gas can or siphon hose to help you out...

Funny, on the five GSes that hang around my garage, the fuel gauge is rather accurate.

I have seen too much variation in miles before going to REServe, so I don't trust that method AT ALL.

The 650L has a smaller tank, it hits RES at about 120 miles.
The 850L has the larger tank, it hits RES at about 140-150 miles.
The other two 850s hit RES at well over 175.
I have not ridden the 1000 (or talked with the sons that ride it) to see how far it goes on a tank.

Regardless, the level shown on the gauge is reasonably accurate. Yeah, it stays above "FULL" for the first 50 miles or so, but then drops quite linearly until you have to turn it to RES as it hits the red mark on the gauge.

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[chuck hahn]

Closely look at the connectors where the wires crimp into them...especially the female ones. Youve got a drop in voltage. I had one do this and discovered the problem was that the wires had some broken strands from several unplugging cycles. New ends solved my problem. Hope it works for you.

[chuck hahn]

Basically how the system works is this. The guage in the dash has a bimetal strip that heats up and flexes which moves the indicator needle. The coil in the sending unit is a rheistat. As the arm moves the metal thing up and down the coil, the lenght of the coils it touches allows a certain amount of current ( voltage ) to pass. The bimetal strip in the guage will heat up a little or a lot depending on where the coils contacted at, thus moving the guage acordingly. Now if the rheistat is dirty, theres some broken wires at the wiring harness connectors, dirty harness connectors you will get bad voltage readings to the guage. Also when you have the cover off the sending unit be sure the arm contacts SOLIDLY all the way up and down the rheistat coil.



Now how to calibrate the sending unit... Leave the cover off the sending unit and reinstall in tank. See what the fuel capacity is in the manual and get exactly half a tanks worth in a can and dump it in. Give the guage a good 2 minutes to equalize and see if the guage is on the half tank mark. If not, then drain the gas back into the can and remove the sending unit. Take some pliers and tweek the square brass nut a very tiny bit and then repeat the process till you get the needle to read half a tank ( while on the bike in its normal position). Once you get it set, drain the tank, reinstall the cover on the sending unit, and i usually add a small bead of permatex formula 2 to the gasket just to be sure the sending unit seals good. The reason you leave the sending unit cover off while adjusting is that youll bend the little tabs on the cover too much and snap them off.

[Steve]

That's a really great way to know when you have half a tank, but let's face it, with half a tank, we are not getting ready to push the bike.

I prefer to follow the FAA (Federal Aviation Administration) requirement for calibrating the fuel gauge. They also require calibration at just one point, but that point is EMPTY. It does not really matter if the gauge stays on the FULL mark for 3/4 of the tank, then plummets to the bottom, but when the tank runs dry, the gauge should show EMPTY.

Actually, I modify that just a bit. I prefer to drain the tank by using the RUN function of the petcock, down to where I have to select REServe. I verify (and adjust, if necessary) that the gauge is at the top of the red zone of the gauge. By adjusting it that way, you can tell when you are approaching REServe, and you can see how far into it you are, once you have switched.

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[chuck hahn]

Steve...it will read full too and you can still put another 1/2 gallon in. And at "empty" you dont know for sure the arm is resting fully on the bottom tab...I say that if you have a known amount that equals excatly half a tank and the needle reads half a tank then your 100% sure without question the system is calibrated. Its like carbs cleaning. You wanna be sure or throw darts in the dark????

[Smellii]

I didn't even see the tutorial on the site. (little red-faced) but I have a feeling both of you are right. I suppose it doesn't matter where you calibrate it from as long as you are sure the gauge matches the proportionate amount of gas in the tank. This info is GOLDEN! Going to try a method and see how it goes. Thanks, guys.