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[Rsantucc]

How do gas gauges show inaccurate readings. Is there a preventative way for us to follow so that we do not fall into this issue?

[JCZ]

I never have (and never would) measure fuel stops by a gas gauge on a motorcycle.  Perhaps it's just old habits not fading easily.  But it's much safer to just know how far I've gone.

This is my method, too.  I have run it where the guage run a tad bit below the "E".  I just pay closer attention to the actual miles driven.......although that varied by about 15 miles, the two times that I ran out of gas.  Just really depends on how hard I'm twisting the wick and wether I'm headed up the grade or down it.

[tony1968]

This happened to my bike, I took in and they tried to adjust it and it didnt work so they replaced the whole fuel pump assy. It has worked every since. All covered.  

[grc]

The adjustment can be done by yourself by bleeding the pressure from the fuel line (pull fuel pump fuse and crank engine several times), then remove the "dash" and the canopy under it.  The tricky part is cutting the clamp on the fuel line to the pressure regulator without dropping pieces into the tank, and then having the ability to install a new clamp when you're finished.  Once the fuel line is removed and the fuel pump/regulator/sending unit assembly is removed, you can then bend the float rod to raise the float to lower the gauge reading.  Unfortunately, this is a trial and error method.  Also, it does nothing the fix the fact that the gauge is non-linear.  On previous bikes, I've done this to make the gauge read slightly above empty when it was time to go to reserve (carb bikes).  On this bike I plan to set it to about 1/8th with one gallon remaining.  

If you are more comfortable playing with wiring, it may also be possible to add a resistor into the circuit from the sending unit to the gauge to lower the readings.  Once again, it won't fix the non-linearity, but at least you can make the last 1/3 more accurate.  I'm planning to look into this once I get the electrical manual.

I haven't gotten around to adjusting the float yet, but I did try adding an adjustable resister into the circuit from the sending unit to the gauge.  Increased the resistance with a full tank to the point that the needle just touched the 'F' rather than lay hard on the peg.  On the first tank, much better correlation with reality.  I average 38 mpg, so 5 gallons gives me 190 miles range.  Now the gauge is at 1/2 at 100 miles, used to be 140 to 150.  1/4 comes in at 150 miles, and the low fuel light comes on at 155 miles.  Now I just have to see how repeatable this is over the next few tanks.

[Coolbreeze]

How much fuel is supposed to be left when you get the "low fuel" light? [smiley=confused5.gif]

[ggraves427]

Where would a person go to get one of them there adjustable resisters, ie. what do we ask for.   A photo showing where the wire is with your resister on it  would bring tears to my eyes. Pleaaassseee!  If I run into any trouble would it be OK if I came to your house and  let you do the whole thing while I drink beer out of your refrig.  [smiley=drink.gif]   Anyway one more post and you you will be a full 100% member or something like that.

[fxdjerry]

How much fuel is supposed to be left when you get the "low fuel" light? [smiley=confused5.gif]

That's probably going to vary bike to bike. Hard to see, dim and sometimes hidden behind the needle. Seems stupid but usually check odometer to see if the fuel idiot light came on. I think I've checked around 150 mi or more  which means i got like agallon left. Most I ever put in at a stop was 4.8 gallons new york thru way asleep before  i noticed. On highways i could use a buzzer or maybe a talking fuel guage. Maybe it says" you will have to push in the next 10 mi if you don't stop for gas". I agree that 150 mi fill is better on the the nerves.

[spydglide]

Each model will usually tell you in the owner's manual.  It varies, but is usually around 1/2 gallon.     [smiley=drink.gif]   spyder

[Twolanerider]

You can also do like I did the first time I didn't realize the low fuel light had come on.  Off on a two lane road someplace not paying quite enough attention and didn't realize that if you're going 60 mph the bottom of the speedo needle pretty well covers the low fuel idiot light.

[grc]

How much fuel is supposed to be left when you get the "low fuel" light? [smiley=confused5.gif]

Per H-D, the low fuel light should come on with 0.9 gallons remaining.  Real funny - my first fillup after buying the bike was 5.2 gallons, and that was less than 10 miles after the light came on.  Must have gotten really lousy mileage on that last gallon.   [smiley=nixweiss.gif]

Jerry

[grc]

Where would a person go to get one of them there adjustable resisters, ie. what do we ask for.   A photo showing where the wire is with your resister on it  would bring tears to my eyes. Pleaaassseee!  If I run into any trouble would it be OK if I came to your house and  let you do the whole thing while I drink beer out of your refrig.  [smiley=drink.gif]   Anyway one more post and you you will be a full 100% member or something like that.

I wanted to run at least one more tank through before putting out the details, just in case I'm overlooking something.  What I used is called a trim potentiometer.  It can be wired as a variable resistor - some may remember the now seldom used term "rheostat".  This particular trim pot is a rectangular device with three wires on one end and an adjustment screw on the other.  The trick was finding one with wire leads, since most are made to be soldered to a circuit board. I'll post details and photos tonight from my home computer.  Of course, you can also just use regular automotive fixed value resistors once you determine how much additional resistance you need.

This whole thing was much easier on my carb bikes - just pull the sending unit and tweak the float arm, maybe 10 to 20 minutes tops.  Now with the fuel pump/regulator/sending unit all together, you're talking a major pain in the butt.  Especially since you will have to do it several times (trial and error) to get it where you want it.

Jerry

[Bad Daddy]

Glad to hear I'm not alone in this.  On the way to Laconia last month, I made the mistake of pushing it one exit too far and ran out of gas with the gauge reading one full tick above the "E".  Now I know where empty really is on this beast and fill up before I get to the quarter mark.  Fortunately I carry a cheap siphon.  It was worth the two bucks!

[grc]

I'm thinking about sending the MoCo a suggestion concerning their "fool" gauges.  Since it would probably be a cost reduction for them, they might just buy the idea.  Aircraft owners or hobbyists will know exactly what this is:

Sight Gauge

[e4seter]

My Gauge works very  [smiley=huepfenjump3.gif]consistant.  

3/4 = 100 miles
1/2 = 130 miles
1/4 = 150 miles
warning light = 170 miles

fill up = 4.7 gallons = 36.1 mpg

PCIII 2 into 1 pipe and SE air kit and I ride fast.  usually 85 on the highways and I love to jack rabbit start in the city.

[grc]

Where would a person go to get one of them there adjustable resisters, ie. what do we ask for.   A photo showing where the wire is with your resister on it  would bring tears to my eyes. Pleaaassseee!  If I run into any trouble would it be OK if I came to your house and  let you do the whole thing while I drink beer out of your refrig.  [smiley=drink.gif]   Anyway one more post and you you will be a full 100% member or something like that.

OK - the parts I used are as follows:  1- 50 ohm trim pot, p/n RWV-42-9-112500 from Surplus Sales of Nebraska http://www.surplussales.com/Potentiometers/Pots-15.html  
1- male terminal p/n 73190-96 & 1- female terminal p/n 73191-96, both from H-D.  The terminals are not necessary if you want to cut and splice, I used the terminals to make it easier to go back to stock if it didn't work the way I thought it would.

Remove the seat and locate the 3 wire connector just aft of the fuel tank (see photo).  The wire you want is the center wire in the connector, yellow with a white stripe.  Pick a convenient place along this yellow/white wire to cut the wire.  The potentiometer has 3 wires, red, yellow, and green.  You will need to connect the red wire and green wire to one end of the sending unit wire, and the yellow pot wire to the other end of the sending unit wire to complete the circuit.  I prefer solder and shrink tubing for this type of splice rather than crimp connectors.  Once the splices are completed and insulated, find a protected location for the pot and either secure it with tie straps or double sided mounting tape (see photo's for my choice of location).  Tape or strap the wires to prevent damage.

To make the initial adjustment, I had the tank full and turned the pot screw until the gauge needle was just touching the left side of the "F" (normal was hard against the peg past the full position).  This gave me the result I wanted, which was to have the gauge read 1/4 with slightly more than a gallon remaining.  Each individual will probably have a different preference, and the nice thing about this method is that it only takes a few turns of the screw to customize the gauge reading.  Be aware that if you add more resistance to give a bigger "reserve" cushion, your gauge will not read full when full.

You can also just splice in a regular resistor (non-adjustable) to lower your gauge reading if you know how many ohms you wish to add.  I measured my resistance after adjusting the pot and found that I had added 7 ohms to the circuit to get the results I wanted.