Motorcycle Pod Filters vs. Air Box: A Buyer’s Guide

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Every motorcycle comes with an air filter or air box.  Over the years, many people switched to smaller, better-looking pod filters instead of the bulky black airboxes.  There are three main differences between pod filters and air boxes; you’ll need to consider these three things if you’re caught deciding between the two.

What are the differences between pod filters and air boxes? Compare to pod filters An air box controls how much air is getting into the carburetors. Although a pod filter does do some filtering, an engine with an airbox is more efficient.

I have owned many motorcycles, some with air boxes and some with pod filters so I’ve been able to get a good idea about how each of them work. As an engineer, I feel compelled to thank the engineers who originally designed the airboxes.  They were designed for a purpose. Changes that improve the appearance of a motorcycle, but have the potential to cause damage to the internals should not be made.

I understand that the original air boxes were bulky and ugly. They serve many functions and protect your engine against serious damage. I love the look of pod filters, but most of them aren’t near as good as an air box.  You can find some of my recommendations below.

An Airbox controls how much air is getting into the Carburetors

I’m a nerd and enjoy learning the technical explanations behind why things work the way they do, so I’ll try to explain some of these chemical and fluid properties as simply as I can so that everyone can understand why air boxes are superior in function to pod filters.  It all boils down to stoichiometry. This is the measurement of air flow in CFM. Let me explain.

Campfires are a great example that I love to share with people.  Many of us have been around campfires at night. The fire is getting too low, so we add some wood to the fire.  This is called stoichiometry. For the flame to continue to burn, it must have a balance between air and fuel.

This is true for all internal combustion engines on cars and motorcycles.  In other words, if you have too much gas, the spark plug will not light the gas. “flooded” The engine.  I’m sure most of you have heard that term, and now you know what it means. It is too much gas in your combustion chamber to ignite and not enough oxygen. For a tutorial on how to clean your engine if it is flooded, see my article here.

The ideal stoichiometric ratio for combustion engines is 14.7 parts fuel to air. Also known as the air-to-fuel ratio.  You need 14.7 molecules to fuel every molecule in your combustion chamber. It doesn’t have to be exactly 14.7 in order to start and run, that’s just the best value to shoot for. It is known as running rich if you have too many gas. You can also call it running lean when you have too much gas.

It is possible for the engine to run lean. The gas could explode too early in the combustion chamber and cause engine knocking and excessive heat.  Running your engine rich isn’t necessarily dangerous, it will just cause your engine to run sluggish and you’ll go through a lot more gas than needed. You can click here to read my article on how to fix a motorcycle that is running rich.

Once you’ve owned your motorcycle for a while and you’re used to it’s little quirks you’ll be able to tell if it’s running lean or rich by the sound and smell of the exhaust when it’s running. Now that you know the basics of stoichiometry as well as air to fuel ratios, I can show you how it relates to pod filters vs air boxes.

An air box purchased from the factory has small openings inside that allow air to be pulled in from the outside. This air is routed through small passageways through an air filter and then into your carburetors. These tiny openings and the air filter are crucial because they reduce the amount of air being pulled into the carburetors.

The cheap pod filters that you see on a lot of café racers, scramblers, and trackers on today’s motorcycles really do look cool, but they have WAY bigger openings on them than the original airboxes, which lets in the maximum amount of air constantly.

If you have 2-3x as much air available but not the same fuel, then your fuel to air ratio is off. Your fuel will not burn in the combustion chamber the way it should. You’re losing out on large amounts of power for the sake of looking a bit cooler.

Air boxes have an integrated air filter

The two main purposes of the air filter in an air box are:  It slows down the air flow inside the air box, and it cleans out all the dust and junk in the air that you don’t want getting inside your engine.

Most pod filters don’t have a filter built in. They may use the word “filter” Pod filters are described online in the product description. However, small stones are what pod filters will keep out from your engine. They won’t stop dust.

Air filters are designed to slow down air flow in the air box.  This goes back to the earlier point. You don’t want the maximum amount of air getting rushed through the air box, you want it to be somewhat restricted so your air to fuel ratio stays as close to 14.7 as possible. Air flow is slowed down by the mesh/foam material that filters are made from inside air boxes.

An air filter’s second function is to prevent dust and particles getting in your engine and carburetor. Air filters are tiny passageways that the air must navigate in order to reach the carburetor.

A filter that is good will have many micro-turns so that the air touches the foam’s edges constantly. This helps to trap dirt and dust particles.

As we have already mentioned, pod filters are terrible at capturing dirt and dust particles.  Most pod filters have only one layer of wire mesh, and no foam. The wire mesh will not stop dust getting in your engine and carbs.  No matter how cool it looks, they aren’t near as efficient with filtering the air.

Let’s talk about what dirt and dust inside your carburetor can do.  Carburetors contain a lot of tiny passages where gas is supposed and can get clogged quickly by dirt. Literally, one little bit of dirt can block a carb and cause it to run badly.

Worst case scenario: Dirt gets through your carburetor’s pod filter and into your engine.  When dirt gets into the combustion chamber it obviously can’t burn, it just gets hotter and hotter.

Hot dirt in your combustion chamber can stick to your piston and cylinder walls.  The hot dirt sticks to the engine wall and then breaks off. The result is usually a loud bang followed by a costly trip to the mechanic to have the top end rebuilt.

Click here to view my recommendations for creative ways to get your motorcycle towed if you’ve been stuck due to engine problems.

Protect your engine from water infiltration with air boxesSide

This is the most important reason air boxes are better than pod filters. Because of the way that air box passages are designed, it’s almost impossible for water to get into the motorcycle combustion chamber unless the motorcycle was completely flooded with water.

Water in your engine can be very dangerous. You should not attempt to start it if there is any. Before you try to start the motorcycle, remove all water from the spark plugs.

Allow me to geek out for a moment and tell you why water in your combustion chamber is so dangerous.  It can cause your motorcycle to stall if it is contaminated by water.

Imagine riding your motorcycle in the rain and then stalling. Riding a motorcycle in the rain is dangerous enough, now you’re adding in another factor of safety since you’ll now need to try to merge through traffic and pull over.  Water doesn’t combust and won’t keep your engine running. Most people know this, but you’d be surprised how many times I’ve had this conversation with people.

A second reason water in your combustion chamber could be dangerous is that it boils when heated and turns to steam. Because steam has a larger volume than liquid water, the gas takes up more space than the liquid.

There’s very limited space inside the combustion chamber as the piston moves up and down, so now you have a superheated vapor trying to take up as much of that space as possible, as well as the burnt fuel vapor also trying to take up the same amount of space, which drastically increases the pressure on top of your piston.

Too much pressure can lead to piston cracks, burned piston rings, bent intake and exhaust valves, and head gasket ruptures.  All of these are costly fixes. The money isn’t the big concern though, your safety is.

You don’t want to ride down a road with an engine failure. This can cause you to fall off your motorcycle and into the path a vehicle. You can read more about how water affects motorcycles in this article that I wrote.

So my question to everyone is: Why would you trust your personal safety to a $5 metal mesh pod filter that doesn’t really filter anything?

If You’re Going To Use Pod Filters

I understand pod filters are better than air boxes.  They’re minimalistic, shiny, and help achieve that open-frame look that so many people are going for right now. I’ve used them several times myself.

But if I can’t convince you to keep your air box then the second best option is to get a better quality pod filter that actually has a foam filter inside. This won’t take away the risk of water getting in or having an incorrect air to fuel ratio, but it will take away the dust and dirt risk.

If you still go with pod filters, here are some pointers to help you make sure you don’t ruin your engine.

Always use grocery bags to cover your bike’s pod filters when washing it. Never ride in the rain! Keep in mind that even a tiny amount of water can cause hydrolocking or a pressure explosion.

The only option to improve the ratio of air and fuel after installing pod filters is to make your carburetor have larger fuel jets.  Because more air is coming in, you will need to add some fuel. Although this does not fix the problem, it can make things easier.

A jet is a small cylindrical metal piece that flows gas through your carburetor. You’ll need to remove the carburetor from the motorcycle and take it apart to install the larger fuel jets.

You may have noticed that some of the motorcycles I show on my blog have pod filters. Yes, pod filters have been used before. However, that is what makes me so knowledgeable about the differences between them and an Air Box.

Similar Questions

My motorcycle is running slow and sluggish. A dirty carburetor almost always causes poor throttle response and slow acceleration.  Many people don’t realize that routine carb cleaning can be a time-saver. It solves many problems such as slow acceleration and throttle response.

How do I remove dirt and water from my engine? Do not attempt to start your engine if you are certain that something has passed through your carburetor.  Take out the spark plugs. You can try to remove it with a small vacuum hose or a flexible magnet. If it is not possible, take the motorcycle to a mechanic.

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