Are your inbound links using Dirt Bike Trails as the link text. This will optimize your links a bit further and give you that last bit of juice.
I did a quick look via Yahoo Site Explorer at your links and your EZ Article is just linked using the URL itself.
Click here to view an article on dirt bike trails and protection.
http://motocrosshideout.com/dirt-bike-trails/
You should change that to "Dirt Bike Trails".
Other things to check:
-Are your backlinks do follow?
-Have you done some competitive analysis of the other pages that are currently ranking? I love Market Samurai for this. Maybe they have twice as many backlinks.
-Finally what is the PR of that URL? Maybe it is conderably lower than the competing top 10