Gas gauge drops as speed increases

[koolaid_kid]

Just remember, it is an estimator, not a gauge.

[tkent02]

I bet you are missing some bit of rubber that is suppsed to keep air out of the gauge.

[Grimly]

Is the fuel gauge circuit stabilised? I don't recall whether there's a stabiliser in the circuit and it doesn't ring a bell, at all. Certainly, on unstabilised car fuel gauges the needle shimmies and shakes like a crack addict, so you can tell whether one is fitted or not, but the Suzuki gauge is fairly slow-moving/reacting as standard, which raises the question if one is fitted or not. If there's one in place it might be the source of problems.

[Steve]

All mine seem to do it and I attribute it to the air rushing thru the back of the gauges and cooling the bimetal strip that actuates the needle itself.

I have never heard of a bimetal strip in the fuel gauge circuit. The only bimetal strip that I know of on a GS is in the turn signal flasher.

I am wondering if the increased amp flow at higher RPM's makes the gauge drop. I need to test it sitting still and see if the gauge drops with voltage rise.

This would make sense, except for one small detail. See the following comment for details.

Is the fuel gauge circuit stabilised? I don't recall whether there's a stabiliser in the circuit and it doesn't ring a bell, at all.

As I understand it, there is a 7-volt regulator that is built into the fuel gauge. Because it runs on a steady 7 volts, it will not be affected by any changes in the charging system. At least not until your system voltage gets below 7 volts, but by the time that happens, fuel gauge accuracy will be among the LEAST of your concerns.

Because of the way the float in the tank works, and the position of the float in the tank, it is susceptible to steep hills and brisk acceleration, but all of the gauges on our GSes are very slow to respond, and I would never notice a drop of 1/4 tank by the time I got to 70 mph.

Also, while I can understand a quick-responding gauge that would drop 1/4 tank during acceleration, what happens while you maintain a steady 70 mph? Does it stay at the lower reading? If it does, does it then go back up when you slow down? If it does, it is related to road speed or engine speed? Try this: at 70 mph, while the gauge is reading lower, pull the clutch, let the engine idle. If the gauge stays low, it's not charging system related.

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[rustybronco]

That particular year uses a magnetic gauge movement whereas some of the earlier years used a bi-metallic gauge that was temperature compensated.

[Steve]

That particular year uses a magnetic gauge movement whereas some of the earlier years used a bi-metallic gauge that was temperature compensated.

Thanks, Rusty, I learn something new every day.

Is it possible that it's another one of those little differences between the chain and shaft bikes?

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[rustybronco]

My 78 GS1000E uses a bi-mettalic gauge so I don't think that is it. It is my belief all fuel gauges before 1982 were bi-metallic and above were magnetic, although I haven't checked each and every model.

[Red1100E]

re

I still haven't dug into it, I will post what I find. Thanks for the input.