Project WideOpen YFZ EHS Custom Airbox Cover "Outerwears"

Aug. 01, 2005 By Justin Waters

One of the first things that many people do to get a little bit more performance out of their ATV's is change something with their air box and air-filter. Many people at first remove the lid and change their jetting which is an easy thing to get just a little more power. Many people go farther and order an after-market filter like K&N. Some people, like me, decide none of that is enough, and order a kit from GYT-R that allows them to run an even bigger air-filter in their stock air box. All of these modifications do have a downside in the long run, one way or another.

Since I've had my YFZ, I've gone through airbox after airbox. I've tried keeping the stock airbox, I've tried 5 or 6 different after-market aluminum airboxes and nothing has seemed to work very well. The aluminum boxes I tried allowed me to run a 250R air filter, which got me more air, but the box mounts broke all the time. There is so much flex in the YFZ frame that I would break a tab or two that holds the box down about every three races. I eventually ended up going back to the stock box.

I finally got tired of trying to find the right combination of stuff to get the performance I wanted that would last and I ended up calling our motor builder at Rossier Engineering. He had done a couple dyno tests with some stuff and recommended what I should do. He said that I should keep my larger GYT-R filter, but stopping running an outerwear directly on it. Instead I should run EHS Racing custom air box cover. In his tests, the YFZ using the EHS air box lid showed a couple more horsepower than the same filter with an outwear and no lid on the box.

The stock airbox lid on the left, and the EHS Outerwear on the right
Take the outerwear off your filter, and let it breathe

I can't say that I can feel the power difference on my ATV because of the work we have done to it so far, but I'm sure on a stock quad you would be able to feel the difference in power. The EHS filter also seems to keep my air filter much cleaner than an outerwear did. It's a lot easier to clean the EHS filter than any other kind of filter too. The filter is made from a water-resistant material so that you can't get water in your air box when its on, but it does make the filter tougher to clean. Since water won't go through it, you can't just wash the dirt out the other side. It does come clean though - just take the whole lid off and wash it in the sink.

One thing you have to be careful of with this product is to not rip it. If you aren't careful during cleaning or installing, you could easily rip the filter. But if you do accidentally rip it, EHS racing has designed the lid so that you can easily replace the filter part with a new one in one of many colors for $15.

You can purchase the lid a couple different ways. You can buy the complete kit that comes with a new lid and the filter already installed in it for $90. If you don't want to spend quite that much, they also sell a kit for $70. Instructions and the hardware you parts you need to make the lid yourself come in it.

Project Sponsors:, Yamaha, Adapt Racing, Douglas Wheels, Elka, Epic Suspension, GYT-R, Kenda Tires, OMF, Precision Concepts, Rossier Engineering, Quadtech, Spyder, Streamline Performance Braking, Tag, Team Industries, TM Designworks, UM Performance, WebCam, Zip-Ty
Racing Sponsors:, CYCRA, Motorex, MXCulture, Scott, SkorBordz

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