5 Reasons Your Harley-Davidson Motorcycle May Be Backfiring

Even if you own one of the best Harley-Davidson motorcycles ever made, you're likely to still experience some backfiring from time to time. Backfiring is a loud popping or cracking sound that erupts from a vehicle's exhaust while driving. It's an unsettling noise for everyone around, but especially the vehicle's owner. Like any other vehicle, Harley-Davidson motorcycles are prone to backfiring. It's especially common in older motorcycles that have carburetor engines. Newer bikes use fuel-injection, resulting in fewer instances of backfiring, but it does still happen. As long as riders keep up with maintenance on their Harley, it shouldn't experience excessive backfiring.

Some owners appreciate the sound of their Harley backfiring, and they might not want it fixed. There's such a thing as too much, though. If it's a constant occurrence, then it's probably time to have a mechanic look at it. There are a number of reasons a Harley might backfire, and it's commonly because of the fuel mixture or something isn't right with the exhaust system. However, there are some other causes. If backfiring happens during acceleration, the cause could be different from backfiring during deceleration. Keep reading to see some of the causes of a backfiring Harley-Davidson.

While backfiring isn't as common with a fuel-injection engine, it does still happen. If the fuel mixture in a Harley is too rich, it can cause some fuel to get through without burning. That fuel ends up getting through to the exhaust system where it ignites, erupting in the loud pop of a backfire. This can happen if there's a faulty injector or bad oxygen sensor.

For those riding a carburetor engine, the carburetor needs to be properly adjusted to the fuel being put in the bike. If it's not adjusted correctly, it's going to let too much fuel get to the engine, which overflows to the exhaust system because it's just too much for the engine to burn.

If you notice your Harley backfiring during deceleration, fuel mixture is one potential cause for it. The fuel mixture needs to be right, otherwise it will get through the engine without burning and instead erupt in the exhaust system. If you don't know what to look for yourself, it's worth bringing the bike in to a mechanic. Either the carburetor will need an adjustment or the fuel injection system will have to be replaced or repaired.

Fuel filters are used in vehicles to keep contaminates out of the fuel. It's recommended that you replace the fuel filter on your Harley every year or 20k miles, whichever comes first. However, this is a general rule of thumb. The Harley you ride might require a replacement more or less frequently.

If the fuel filter is too old or damaged, it's going to let impurities through, contaminating the fuel. One of the common side effects from a bad fuel filter is, you guessed it, backfiring. The contaminates that get into the fuel are going to prevent the engine from igniting it properly.

Additionally, if debris gets stuck in the fuel filter, it can obstruct the proper flow of fuel into the engine. Luckily, a fuel filter is easy enough to change out without needing a mechanic and is a must-know maintenance tip for motorcycle owners. Keep up with maintaining the fuel filter and this will rarely be an issue. 

Spark plugs, as the name suggests, generate a spark that ignites the air-fuel mixture in the engine to generate power to the rest of the motorcycle. They're an important component to all ICE vehicles. When the spark plugs don't fire correctly, they fail to ignite all of the fuel in the cylinders. Sometimes older spark plugs won't generate enough heat to combust the fuel, which leads to an uneven combustion and unburned fuel. That unburned fuel gets through the engine and into the exhaust system, where it will ignite the moment it comes into contact with the hot exhaust pipes.

Be sure to always check the spark plugs to see if they're old or degrading. The only way for you or a mechanic to tell if a spark plug is bad is to remove it from the engine. Burned insulator tips or discoloration are signs that the spark plugs aren't working properly and need to be replaced. Backfiring isn't the only issue from faulty spark plugs. If there's an unstable ignition, it can also lead to bad fuel efficiency and a reduced lifespan for the engine overall.

Motorcycle owners love upgrading their bikes because it's more than a simple form of transportation for them — it's an extension of their personality. There's a slew of potential customization types for motorcycles, from purely cosmetic upgrades to performance modifications. One of the more popular aftermarket modifications Harley owners go with is a modified exhaust system, as it can change the entire look of the bike as well as improve its performance.

However, if an exhaust system isn't properly installed, it can lead to a slew of problems, including poor exhaust flow and backfiring. Since aftermarket parts aren't designed by the bike's original manufacturer and aren't fitted for the bike's standard jetting, it's going to need proper fitting and tuning before the owner takes it home to show off. Even if you're going to have non-exhaust related mods done to your Harley-Davidson, go to an experienced technician. They can ensure everything running as it should be.

There are a couple carburetor issues that can cause some backfiring, but a dirty one is the leading cause. The carburetor can collect dirt and debris as time goes on, which serve as obstacles for fuel to get through to the engine. When fuel can't flow through the carburetor as seamlessly as intended, it's going to lead to a lean-running engine. How often should you clean your bike's carburetor? There's no definitive rule, but once a year is a good start. If your motorcycle is your primary mode of transportation, then possibly more frequently than that.

Fuel injection motorcycles don't run into this problem nearly as often, but it can happen if the fuel pump has a problem or the injectors are dirty. Dirty injectors are not an uncommon cause for frequent backfiring. So, it's important to keep the injector clean. Oftentimes, the owner's manual will have a recommended cleaner to use. Inspect the fuel pump as well to make sure it's not damaged. If it's not, sometimes it will need a replacement to fix the issue.