fuel gauge calibration?

[Guest]

Not sure if this is the right place. Fuel gauge on my 1980 GS1000G goes from full to about 1/2 tank
at 30-40 miles. ANNOYING. Then down to a quarter tank over the next approximately 100 miles.
Has anyone figured out how to calibrate the sending unit so it reads a bit more accurately? I do set
the trip odometer at every fill up but watching my gauge go to 1/2 tank in 30 miles is... well annoying.

[posplayr]

You can remove the sender and inspect it to see if there are gaps in the wiping area of the slide. The material the board is made of can distort with age and cause the wiper to not be linear.

[Steve]

Sometimes it's just a matter of cleaning some crud off the windings or the wiper. Might not look like much is on there, but some careful wiping will clean it off.

Since you are playing with the sending unit anyway, why not adjust it to match the gauge, too?

I will start with about half a tank, run a hose from the petcock to a can sitting beside the bike. Apply vacuum to open the petcock in the RUN position, let the tank drain into the can. Turn the key ON, watch the gauge as it goes down. (It helps the battery a bit if you turn the "kill" switch OFF and pull the headlight fuse.) When the gas stops flowing, note where the needle is on the fuel gauge. Personally, I like to see it right at the beginning of the red zone as it needs to be switched to REServe. If the needle is not pointing there, you can remove the sending unit and bend the arm a bit, but remember to bend it opposite what would seem normal. If the needle is into the red zone when the gas stops flowing, bend the float arm DOWN, which will raise the position of the needle. You might have to go through this procedure a couple of times before you get to a comfortable position on the gauge, but this is the only time you will have to do it (on this bike).

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[alke46]

I had the same problem on my bike. Just cleaned the wiper and did the resistance check on it and it all started working like new again. Didn't need to adjust the float level at all.
I can't remember where I found the resistance values now but I know it was somewhere in the FSM.
Maybe someone else will chime in and tell you where to find it.
Mine now works with accuracy that I can count on. Good luck.

[geol]

Which part is the wiper?

[alke46]

It's the small fibre looking piece with smallish wire wrapped around it.

[geol]

I haven't taken the thing out of the tank at this point so will post a pic of the fuel float assy. If you could
tell me what number from the diagram, it would be helpful. Thanks

[Steve]

#10 is the actual sending unit, it contains both the coil and the wiper, neither of which you can see in that drawing.

Once you open it up, it's readily apparent which is "coil" and which is "wiper". The wiper is the part that moves (wipes) across the coil.

If you look at the wiper arm, you should be able to see how you can bend it just a bit to add a little bit of tension, so it makes better contact on the coil. Sometimes that is all that is necessary to get it to work correctly.

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[geol]

Thanks Steve. That part looks strangely similar to the arm on a vintage KZ with a gas gauge... I have had several KZ1000E (shaft drives) that had these similar arms and will check to see if it is actually the same when I have it apart. Unfortunately, none of the Kaw gas gauges I have had on my bikes in the past were very accurate either but not nearly as bad as the one on this GS I now have. I will probably take a day next week to look into it. Thanks!

[geol]

One thing I should have asked... if I take the sending unit out, what type gasket is used and is it typically re-usable or do I need a new one on hand to keep the thing from leaking when the send unit is re-installed?

[Steve]

It's a rubber gasket, should be able to re-use it with no problem.

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[chuck hahn]

Once you have verified the board and the slider arm makes constant contact throughout its rage of motion, heres how i set them up. I first look and see what the manual says is the fuel capacity and get exactly HALF that in a can at the pump.

Now the fiddling part begins. with a drained tank dump in the premeasured amount from the can and turn on the key and let it set a good minute or so to be sure the gauge is 100% settled in. If it reads right on the half hash mark your done. If it reads below the half mark bend the float arm down..if its higher than the mark then bend the arm up. May have to go thru the process a few times till you get it real close to the half full mark.

When my bikes needles just begin to touch the E mark they start to stutter and I need to hit reserve.

[OldVet66]

My gauge is similar to yours, it goes down to half very quickly, but at dead empty on the back side of the empty mark it has 2 1/2-3 gal. left in the tank. I've gotten so used to it I just use it as a reminder that I should get gas within the next 100 miles.

[geol]

OldVet66, You see the positive in everything fella! When I get down below 1/4 tank, I have only managed to ffill about 3 gallons. I am getting about 35 mpg (only checked twice now) and I think I will fiddle with the gauge as has been suggested to get a bit more accuracy! Thanks guys.

[Steve]

When my bikes needles just begin to touch the E mark they start to stutter and I need to hit reserve.

That is the philosophy that I use, I just don't bother with the "exactly half the capacity in a can" first.

My procedure (listed in post #3) is inspired by the FAA's guidelines for aircraft. Their fuel gauges need to be accurate at exactly one point: EMPTY. It doesn't really matter whether it stays on FULL while you go through half a tank, then races to EMPTY, as long as it's accurate at EMPTY.

Since I have the luxury of a REServe part of the tank, I calibrate my gauge so I know when it's going to hit REServe. Once I have turned it to REServe, I know that I have less than 40 miles before I will need to be wearing some comfortable walking shoes. In a nutshell, the white portion of the gauge is the main part of the tank, the red portion is the REServe.

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