Fuel gauge reads low

Datman

Joined
Jun 28, 2026
Messages
2
Age
70
Location
27613
Bike
ST1300
Hi,

I just bought a 2012 ST1300 with 1k miles. Unfortunately the owner let gas sit for most of its life. The upper tank, fuel pump assembly, and sending unit were beyond cleaning. I have replaced all three along with several hoses. The lower tank wasn't too bad.
My problem is the fuel gauge. When I filled up it quickly went to 7 bars and after several minutes the 8th bar lit up. I traveled around 17 miles and it dropped to 7 bars. At around 50 miles it dropped to 6 bars. I've owned other ST's and those gauges gave pretty accurate results. I was careful installing the sending unit so I don't think I bent the arm, but maybe I got a defective (bent) unit from Honda? I've only ridden 50 miles so don't know how it will end.

Any advice on what to check or how to determine if the support rod is bent?

I'll ride to get the gas out of the upper tank. The service manual suggests checking resistance at the meter but that means lots of plastic removal, right?

Thanks, Doug
 
Possibly bent... usually, there are lower tank issues once the gas gets to that level which causing some odd thermister? readings from the lower tank.

Since this is the upper tank I wouldn't worry about it too much. I'd just ride it and after 200 miles do a fill up and do the manual calculations that 200 miles is giving you the mpg you expect.
 
Thanks for the advice. I'm not worried about running out of gas. I owned another ST for 10 years so know their general gas consumption. I haven't ridden far enough yet to get to the lower tank. I assume my brand new fuel pump assembly thermistor will work correctly though.

My issue is I like things to function properly and my upper tank gauge is not. I'd like to fix it. I'm looking for possible steps to diagnose the problem and fix it.
 
Feel your pain; my "new to me" 2010 recently dropped from a full tank to the reserve flashing indication a couple times, which caught me by surprise. I haven't explored the problem yet; likely will do more "on the road" troubleshooting to see if it happens multiple more times, then dig into it over the winter when I install the new McCruise and dual cams I have ready to go. Good luck with yours; let us know what you find out!
 
Datman said:
My issue is I like things to function properly and my upper tank gauge is not. I'd like to fix it. I'm looking for possible steps to diagnose the problem and fix it.
Click to expand...
Since your sending unit is new the most likely cause is that the float arm got bent somewhere.

Remove the sender unit from the fuel tank.

Test 1:
- Connect an Ohmmeter to the gray/black and green/black terminals.
- Move the float arm to the fuel tank full position. The Ohmmeter should read 1 - 6 Ω.
- Move the float arm to the empty fuel tank position. The Ohmmeter should read 213 - 219 Ω.

Test 2:
With ignition switch in the off position connect the sender unit to the motorcycle's wiring harness.
- Move the float arm to the fuel tank full position.
- Turn the ignition switch to the ON position. All eight of the fuel gauge segments should be illuminated.
- Turn the ignition switch to the OFF position.
- Move the float arm to the fuel tank empty position.
- Turn the ignition switch to the ON position. Two fuel gauge segments should be illuminated.
- Turn the ignition switch to the OFF position.

If all of your test results match the above your fuel sender unit is working properly and your fuel gauge is interpreting the fuel sender signals properly. This means that your float arm is bent and needs to be reset so that the it is in the correct position to match the actual fuel level.
 
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