Can you add fuel gauge to older motorcycle?

The problem you face is not the gauge but rather the sending unit in the tank .

If tank was not originally equipped with a sending unit , it will be hard to retrofit one .

Were I trying to accomplish what you want , I'd see if there were a later model tank with a sending unit that would fit that bike .

Like the other poster ,, I have never had a fuel gauge on any bike and I've been riding almost 50 years .

Unlike the other posters I have one bike with a fuel gauge – it is wildly inaccurate and cannot be relied on. I can only imagine how an aftermarket one will be. Better to use a tripmeter.

Could add a sight guage, but will mean drilling holes in your tank.

I have never had an issue without a fuel guage. Even on my daily driver, I pop the cap and look as the float/guage doesn't really do a good job showing the actual fuel level.

With money, maybe lots of money- yes. For practical reasons, just learn to use trip meter and maybe if really worried carry a extra gallon fuel can in tail trunk or milk crate- what I used to do on night runs when stations were likely closed on side routes taken. Goldwing with fuel filler neck under panel annoying to check the under seat tank so fuel gauge was reasonable for market. Latest Suzi has gas gauge that sort of works- relatively small tank so helpful, Miss the old R50/2 with the big tank good for 250+ miles at old 55 cruise speed

Most bikes have saddle tanks. ie. they come down over the top of the frame on both sides. This means it is VERY tricky t ofit a even reasonably accurate fuel gauge. Have had 2 bikes with fuel gauges - one stopped working altogether & the other was near useless. Odometer & reserve tap is a much more reliable way to go.

Each time you fill u preset the trip meter & turn fuel tap OFF reserve. Run bike until it hesitates with fuel starvation turn onto reserve & look for a servo in next 20 miles.

Why? Lol. I've owned several bikes and NONE of them had a fuel gauge. Are you really that incompetent?

Here is what I use to do...

Fill up the tank, set the trip odometer to zero. Drive for a while, and when filling up the tank with gas, make a note of how many gallons you purchased, and the miles you drove. (Example given) 45 miles, 1.5 gallons of gas. Do this several times, and divide the mileage by the gallons to determine your average miles per gallon.

Now, if you can, drain the gas tank, and fill it up to determine the tank capacity. Take your tank capacity, and multiply it by your average miles per gallon. Now, every time you fill up, set your odometer to zero, and note how many miles you have until empty.

Example given: average miles per gallon is 30. Fuel tank takes 2.5 gallons of gas, miles until empty: 90.

You can re-engineer anything with enough time and money. Use a capacitive sender. It works on, like, capacitance, dude. Look up the words you don't know. https://www.google.com/#q=capacitive+fuel+level+se...

No