WHAT IS IT? An innovative air filter design that compensates for the airflow limitations of the 2010 YZ450F’s top-mounted airbox.

$109.95 (aluminum cage and pre-oiled filter), $32.95 (over-the-cage pre-oiled filter), $25.95 (pre-oiled YZ450F replacement filter).

CONTACT? or (559) 651-4120.

Here’s a list of things that stand out with the DT-1 Factory Air Flow kit for the 2010 YZ450F.

(1) The problem. When Yamaha designed the 2010 YZ450F, they couldn’t figure out what to do about the air filter, and as a result, the stock air filter (which is shaped like a jumbo-sized piece of Texas toast) does a very poor job of getting air into the engine. From a scientific point of view, a high-performance motorcycle engine needs 14 times as much air as it does fuel. The stock YZ450F air filter design has serious limitations.

(2) The solution.
Given the limited space available, DT-1 was still able to find a way to increase airflow into the YZ450F. They achieved this by removing the piece of toast and mounting an air filter over (as opposed to under) the YZ450F’s cage. This increased the filter’s surface area by more than 80 percent and gave the clean air side of the filter more volume for the engine to ingest. DT-1 has two YZ450F kits.

(3) Over-the-cage. For $32.95, DT offers a considerably larger air filter that fits over the top of the stock YZ450F plastic cage (although you have to clip off two tabs). The large air filter flows more air because it increases the surface area. It is a simple and easy way to get more air into a YZ450F, but it is not the one that the MXA gang uses.

(4) Factory Air Flow kit.
MXA’s YZ450F uses the factory Air Flow kit. DT-1’s Factory Air Flow kit is the ultimate expression of the over-the-cage filter idea. It consists of two parts: a low-profile aluminum cage and a pre-oiled filter that fits over it. How does the Factory Air Flow kit differ from just using the DT-1’s over-the-cage filter with the stock cage? The kit’s aluminum cage is optimally shaped to not only increase the surface area of the filter (although not as much as the over-the-cage filter), but to allow for a more evenly dispersed air cavity around the outside of the filter. Thus, even though the factory Air Flow kit has less surface area than DT-1’s over-the-cage filter, it flows even more air because its extra space distributes the air better (and there is no chance of the filter foam making contact with the YZ450F air box lid).

(5) Choice. Let’s not beat around the bush. The $110 Factory Air Flow kit works best. It is the exact filter system used by James Stewart, Josh Hill, Jason Lawrence and Grant Langston. That said, the $32.95 over-the-cage filter is no slouch, and both filters are significantly better than the stocker.

(6) Flame-resistant oil.
DT-1 pre-oils all of its filters with its proprietary flame-retardant air filter oil. It will also cut down the backfire consequences of other brands of filters. It retails for $18.95 a liter.

WHAT’S THE SQUAWK? Some of Yamaha’s teams recommends drilling one-inch holes in the radiator shrouds to allow more air into the airbox, but you need to re-map for more fuel if you do this. We cut the holes, remapped and raced the bike. In the end, we taped the holes up because we couldn’t stand the extra noise or the increased air filter maintenance required on dusty tracks.

Simple mods like these are rare in the motocross world. You can choose your poison, but for as little as $32, you can have the same parts that James Stewart runs.

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