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" Any kid who has built a bike jump has probably dreamed of something like a pump track, a loop of banked turns, rollers, and benches that can feel like a perpetual motion machine. Imagine a motocross circuit at one-tenth scale but meant for mountain bikes or a kid&amp;#039;s BMX. When Mark Weir finished the pump track at his home in Marin County, Calif., local kids swarmed\u2014and their dads asked Weir to build tracks in their yards too. Now he is working on a $1 million version for nearby Stafford Lake. &amp;quot;Once you start, you have to realize the addiction that comes with it\u2014all of a sudden you&amp;#039;re more of a builder than a rider,&amp;quot; he says. To get the advice laid out above for DIY builders, we turned to Lee McCormack, who wrote Welcome to Pump Track Nation and has created hundreds of tracks.  MCCORMACK&amp;#039;S TRACK TIPS DESIGN: Avoid flat spots. &amp;quot;Every square inch should tilt up, down, or sideways, to keep momentum going.&amp;quot; SITE: Build on a 3 percent slope to avoid flooding. Got a flat lot? Dig French drains at the berms. CONSTRUCTION: Pile dirt 50 percent higher than the final dimension to account for compaction. Then carve out the contours.&amp;quot;It&amp;#039;s almost impossible to get a nice shape by adding dirt. It&amp;#039;s easier to move it.&amp;quot; MAINTENANCE: Run a sprinkler to lightly soak the track before each ride. Let it nearly dry, and then pedal like crazy to &amp;quot;burn in&amp;quot; a line. RIDING: Ratchet the pedals in short quarter-turns and push down with your arms off the backsides of rollers. Don&amp;#039;t pedal continuously. WORKOUT: The top priority is fun, but pump tracks also build MMA-worthy core strength and balance skills. INPUTS THE DIRT: Clay loam or topsoil mixed with clay is best. A 40 x 30\u2014foot area takes 27 cubic yards.  HAND TOOLS: Wheel-barrow, shovels, string and dowels for layout, a soil tamper. THE MACHINE: Yes, this counts as an excuse to rent an earthmover. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/home/outdoor-projects/a7676/how-to-build-a-backyard-bike-track-8347632/>