How To Pressure Test A Motorcycle Gas Tank?

A lot of riders, myself included, are tempted to drain their motorcycles’ fuel tanks and “refill” them with fresh, expensive premium fuel (such as E85). This is not only dangerous but also unnecessary — if you have an accurate gauge, you’ll see that there isn’t enough room left for more than one or two full gallons of regular unleaded gas. You should empty out your gas tank at least once every three months (or whenever you get around to doing maintenance) so you don’t waste money on overfilled gas tanks.

This brings us back to why we’re going through all these complicated steps above. The short answer is that you want to make sure you haven’t accidentally filled up beyond the maximum amount of usable space. If you fill up past that point, even temporarily, then you run the risk of having some kind of catastrophic failure occur later down the line. In other words, filling too high could cause engine damage or worse yet, lead to costly repairs.

The first step is to find out whether or not you already filled the tank too full. We recommend checking behind your seat where the gas cap would normally be located. If you notice any extra liquid sitting inside the tank then you probably need to take another look under your saddlebags and/or fairing.

Now let’s move forward with our demonstration…

Demonstration #1 – Checking Your Gas Tank Cap

To figure out if you filled your gas tank beyond its intended capacity, here’s what you’ll need to do:

Step 1:

Find your spark arrestor or carburetor cleaner screen. It will either come off the air intake side of the filter housing or somewhere else along the beltline between the front tire and the frame. Once you locate it, pull it towards you slightly and hold it firmly against something sturdy like a wall. Now check underneath where the wire goes into the valve cover. There may be several wires coming from the spark arrestor, depending upon the age of your machine. Make note which one is connected to the ignition system. That’s the one you’ll need to pay attention to. You may have to jiggle the wire loose from whatever connector it comes attached to before you can access the spark arrestor itself.

Step 2:

With the spark arrestor exposed now, you should be able to identify the area right below where the wire attaches to the ignition cylinder. On my Harley-Davidson Sportster Classic I can clearly see a small hole just big enough for the tip of the plastic plug to fit snugly within. Inside this tiny little hole sits a rubber grommet that allows the spark arretter to slide freely without being pinched during normal operation.

Step 3:

Slide down the plastic plug until it pops free of the grommet. Then lift up the end of the spark arrestor to remove the entire assembly entirely. What you’re looking at next is called the “float chamber.” As the name implies, this part contains excess fuel that has nowhere to go except up. And since your bike uses gravity to feed fuel into its combustion chambers, keeping this float chamber full helps ensure proper performance throughout the ride.

Now let’s put everything together again.

Step 4:

Use pliers to gently grip the spark arrestor near the base and twist it counterclockwise about 30 degrees. Keep twisting until most of the slack is taken out. At this point, you should feel resistance and hear a slight click. Congratulations! You’ve successfully removed the old spark arrestor and replaced it with a new one.

In summary, you’re trying to determine whether or not you accidentally overfilled your tank with gas while refilling it last time. By following those four easy steps outlined above you can avoid making a potentially serious mistake. Not only will you save yourself money, you might very well increase your bike’s overall reliability as well.

We hope you found this article helpful.

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