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September 26, 2011
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WHAT IS IT? A completely redesigned airbox and air filter for the 2010 and 2011 YZ450F.


www.twinair.com or (800) 749-2890.

WHAT STANDS OUT? Here’s a list of things that stand out with the Twin Air YZ450F airbox.

(1) Concept. Twin Air has designed a totally new airbox and filter with the goal of getting more airflow into the throttle body. The Powerflow kit includes not only a green weenie-style air filter, but a completely new intake tract.

(2) Installation. Compared to a traditional airbox, the new generation YZ450F airbox is very complex. It has more parts and pieces than a traditional airbox and is hard to work with. To remove the stock airbox and replace it with the Twin Air Powerflow airbox, you have to make some modifications to the stock parts. Luckily, Twin Air’s illustrated instructions helped us figure it out. The details weren’t as clear as they could have been, though, and it took us an hour or so to work out the issues and install the airbox.

(3) Dimensions. The different layout, shapes and sizes of the Twin Air system all play a part in its performance. The Twin Air airbox is deeper, making room for the tall, cylindrical-shaped air filter. To make more room for the air filter, Twin Air takes some length out of the intake tract. More airbox volume means a larger supply of air, and a shorter intake means that the air is drawn into the engine quicker. Amazingly, the Twin Air air filter boasts 97.3 percent more surface area than the YZ450F filter. More surface area means more airflow.

(4) Materials. The ABS plastic air box has holes in it, which are covered up by breathable, removable panels designed to let in air but not dirt. The filter is flame retardant and there is no backfire screen.

(5) Performance.
When we fired up our Twin Air-equipped YZ, we noticed that the irritating motorboat-like sound coming from the YZ450F intake was deeper sounding. We expected a noticeable improvement in power, but the only seat-of-the-pants sensations were that the engine felt freer, revved quicker and sounded better. The real plus of the Twin Air Powerflow kit doesn’t come with the stock exhaust system and fuel mapping, but the ability to hop up the engine and still have enough air flowing through it to allow for more fuel and horsepower. On a stock engine, it has some nice attributes, but with a pipe, head mod or remapping, it could be much better.

(6) Maintenance. Getting to a YZ450F filter is a pain, and it isn’t any easier to get to the Twin Air filter. Once inside, however, maintenance is much easier. We didn’t have to be so worried about knocking dirt into the intake tract, and we could easily wash the entire airbox by using the supplied aluminum intake plug. The new filter never looked as hammered as the stocker after a race, and we felt comfortable riding a little longer before installing a clean one.

(7) Durability. The intake sits on the frame and is connected to the engine, so it vibrates and flexes quite a bit with the bike. The stock unit is made with more pliable, rubbery polyurethane, while the Twin Air is more rigid. Be certain the nut securing the filter is on tightly; it can (and does) vibrate loose. We haven’t had any issues with the Twin Air system, and we don’t expect to, but it’s not as durable as the stocker.
Our beefs aren’t with Twin Air, but with whoever designed the YZ450F airbox in the first place. It is a hassle to work with.

The Twin Air YZ450F Powerflow kit isn’t just a new filter and cage?it’s a major modification that boasts a lot more volume and surface area and is easier to maintain.


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