The air cleaner element, installed in the air cleaner box, is an essential part to keep the engine in good condition by removing dust and foreign substances from the air. The element can be made of non-woven fabric, filter paper, or urethane foam, of which urethane foam has the advantage of being lightweight and can be cleaned and used repeatedly. However, it can disintegrate over time, so regular maintenance is required.
- Whether it is a sponge filter using polyurethane foam or a dry filter using non-woven fabric, a clogged element leads to engine malfunction.
- If the fuel and filter oil that is blown back deteriorates and disintegrates the urethane, it will directly lead to engine malfunction.
- When using a generic filter without OEM parts, choose a product that is not affected by fuel or oil.
Whether it is a sponge filter using polyurethane foam or a dry filter using non-woven fabric, a clogged element leads to engine malfunction.
For 2-stroke moped scooters, which are often used at low speeds around town, primary compression is blown back from the engine crankcase to the carburetor, and a tube (bottom right) is attached to the bottom of the air cleaner box to collect fuel and 2-stroke oil (4-stroke motorcycle also have a tube in the air cleaner box to collect emulsified oil).
Whenever a manufacturer develops a carbureted or fuel-injected vehicle for the market, the air intake system must be set up, and the air cleaner element is an extremely important element in this process. There are three types of elements: the wet type, which uses urethane foam soaked with oil, the dry type, which uses filter paper or non-woven cloth, and the viscous type, which uses filter paper soaked with oil.
When the air that the engine is trying to inhale passes through the element, there is a certain amount of resistance, but the manufacturer has made settings during development that include the entrance to the air cleaner box, the box volume, and the resistance of the air cleaner element. Therefore, if you remove the element only to reduce the air intake resistance without worrying about some foreign matter being absorbed, it may cause the setting to deviate.
Similarly, unnecessarily enlarging the air intake of the air cleaner box may also affect the balance of the intake system. If you are planning to change the setting of the carburetor or injection system, it is better not to remove it just because "it seems to be resisting somehow".
Another problem in the balance of the intake system is a clogged element that prevents the engine from inhaling enough air to meet its needs. It is hard to tell the effect of the element, which gradually gets dirtier as the mileage increases, but in the case of carbureted vehicles, a clogged element will cause the negative pressure generated by the engine to add significantly to the float chamber, resulting in a fuel-air ratio that is thicker with fuel.
In the case of injected vehicles, the ECU may respond to compensate for changes in the pressure in the air cleaner box and the amount of air flowing into the engine, but it is natural for engine power to decrease as the amount of air flowing into the engine decreases.
For tuning and customization enthusiasts, the air cleaner element may be an unnecessary part that should be removed immediately along with the air cleaner box. However, dust and dirt in the air is the engine's worst enemy, and it is just as essential as the masks that we are familiar with today. On the other hand, it is essential to check them regularly, as leaving them on can also trigger a decline in performance.
- Point 1: Regardless of whether the air intake system is wet or dry, the settings of production vehicles are determined on the assumption that an air cleaner element is present.
- Point 2: If the element becomes clogged due to dust and dirt during driving, the air-fuel ratio will change to a darker ratio for carbureted vehicles, so it needs to be cleaned or replaced.
If the fuel and filter oil that is blown back deteriorates and disintegrates the urethane, it will directly lead to engine malfunction.
If the fuel or oil in the tube is left unattended, it will accumulate at the bottom of the air cleaner box, soaking the sponge all the time and causing it to deteriorate. Even if there is no oil puddle, it needs to be checked periodically because it will break down into pieces as it deteriorates over time.
Wet-type elements, which are made of urethane foam (sponge) soaked with oil, are often installed in small displacement vehicles. They are lighter than dry-type elements, which are made of finely bent filter paper assembled on the frame, and their filtration performance does not deteriorate easily even if water adheres to them.
On the other hand, fuel, oil, and organic chemicals can affect the structure of polyurethane foam. Specifically, the sponge itself can easily rip, tear, and disintegrate. Deteriorated sponges break apart like a sponge cake and are suctioned in by the engine's intake air.
In terms of age, urethane foam elements are most commonly found in carbureted motorcycles, and when the disintegrated sponge adheres to the carburetor, it can cause a variety of problems, including inability to start and riding sluggishly. There are no holes in the sponge filter to reduce the intake resistance and improve the engine condition.
Some of the sponges disintegrated by fuel and oil will fluff up like dust, but some will stick to the intake system like sticky pieces of coated sugar candy. They can lodge in the venturi, the air intake passage of the carburetor, or block the fuel outlet. Structurally, a carburetor may look like just a series of small holes, but these holes are used to precisely measure air and fuel.
The owner's manual or service manual instructs to check the condition of the air cleaner element every 6 or 12 months, and to clean and refuel it if necessary, but how many people, other than those who have their motorcycles inspected by a motorcycle store, regularly check the air cleaner element?
In this day and age, there are many people who pull out their scooters that have been left in the corner of the bicycle parking lot for a while and try to ride them, but I strongly recommend that you check the air cleaner element along with the tire pressure.
- Point 1: Urethane foam wet sponge filters deteriorate and disintegrate into tatters due to fuel and oil adhesion and aging.
- Point 2: It is important to maintain the product according to the inspection cycle in the instruction manual and service manual.
When using a generic filter without OEM parts, choose a product that is not affected by fuel or oil.
The filter is so brittle that it can be easily torn apart with a slight twist, but if the outer frame is still intact, you are lucky to be able to copy it onto a generic sponge. If the condition is worse, place a piece of cardboard on the air cleaner box and trace the shape of the filter. If the filter is sandwiched between the box body and the cover, decide on the shape so that there is no gap.
The sponge can be freely deformed so that it can be cut slightly larger than the actual filter and still be pushed into the box. DAYTONA's turbo filter sheet has a double-layered structure with a yellow side with a coarse density sponge and a black side with a fine density sponge, and is generally used with the yellow side facing the intake side of the air cleaner box and the black side facing the carburetor side.
The factory air cleaner element is wetted with filter oil (2-stroke oil) before assembly. However, DAYTONA's turbo filter is a dry type, so no oil is required. If it gets dirty, it can be washed with a mild detergent and reused.
When replacing the air cleaner element, it is safest to get the OEM parts for that model. The air cleaner box usually consists of a case body and a cover, and an OEM element can be installed between the 2 without any gaps. Also, if the part is made of a material that is supplied as OEM parts, it is guaranteed to be durable for a certain period of time.
In contrast, a universal type sponge filter can be used immediately for models for which the OEM parts are no longer available, or without waiting for the OEM parts. If it is a universal material developed for motorcycle air cleaner elements, there is less risk of deterioration due to fuel or oil, and the filtering performance of dust and dirt is also taken into consideration.
One of the typical universal filter sponges is the Turbo Filter made by DAYTONA. This product features both high intake efficiency and filtration performance by layering coarse and fine polyurethane foam nesting materials. It can be easily cut to fit the shape of the air cleaner box, whether it is used as a sheet or wrapped around the frame.
There is no need to worry about sponges developed by motorcycle accessory manufacturers for air cleaner elements, but be careful when using sponges sold at home centers. Even if the material used is polyurethane foam, its durability against fuel and oil varies depending on its composition, and some can deteriorate in a short period of time. If you want to use it for the air cleaner element, choose a sponge that is fuel and oil-resistant.
- Point 1: In contrast to dry type and viscous type air filters, which often use special frames, sponge type filters can often be made from universal products as well as OEM parts.
- Point 2: When using a universal sponge, select an oil- and fuel-resistant sponge that is compatible with the air cleaner element.
