I have an 2004 Heritage Softail. The gas gauge has never read full, even when the tank has just been filled. Always sorta kinda worked from 3/4 down to empty. Always used the odometer as the real gauge. Took off this morning and the gas gauge read about 1/4 (which would be normal for this gauge) and the odometer read 99. I got to the corner and the odometer read 117. Thought I must have misread it. A couple of more miles down the road it is reading 199. I noticed the gas gauge for the first time ever is now reading full. Another four or five miles and the odometer is at 247. Headed home and parked it. Any idea on what has happened and what to look for?

 

..is there a flux capacitor involved...?

I've heard of speedos piling up quicker if it was accidentally toggled to KPH, but not that fast...

 

Check your grounds. From what I've seen in here, anytime gauge fluctuation is occurring, bad electrical grounds are the culprit.
As far as your inaccurate gas gauge, I and maybe one or two other members in here claim to have an accurate gas gauge.
And I still use my trip meter.

 

I'll try to find where the gas gauge grounds. What has me truly baffled is why the trip odometer is suddenly gaining mileage so quickly.