Backyard Dirt Bike Track
Dirt bikes are always fun to ride and once you gain some experience, building a few jumps in your backyard is a natural progression. While a full size motocross track would be great, you'd be surprised how much fun you can have with a few small piles of dirt and how much your riding skills will improve. Any large scale motocross track-building project is best left to the professionals, but a small backyard track is within reach of anyone willing to do a bit of planning and some hard work.
Planning the track: Even though you're building a backyard track, spend a few minutes at the Dirt Wurx website. These are the guys that build the motocross tracks for the pro riders. They've put together an awesome set of tutorials on designing and building a full-size pro motocross or supercross track. Just remember that most of that info is for the pros - don't base your backyard track design on a professional motocross track design. It takes a lot of sweat equity to build any size dirt bike track and also requires quite a bit of pre-planning. Here are a few more things to keep in mind:
Neighbors: If you have neighbors nearby, noise may be an issue. Trail bikes should be fine but motocross bikes, especially the four stroke motocross bikes, might be a potential excessive noise problem. During the dry summer season dust may also become an issue. It may help to put up a fence or tree buffer, but check with your building department to see if there is a setback requirement for the fence and plan the track accordingly. If your property is not surveyed, err on the side of caution and stay well away from the perceived property line or better yet, pay to have the property surveyed.
Liability: Having your own track to practice on is great but riding with friends is much more fun, and if you're thinking of riding competitively in the future you'll need to learn how to deal with other riders while on the track. Accidents can happen, so talk to your insurance agent to find out what your homeowner's policy covers. Consider talking to a lawyer to find out what might happen if someone gets hurt on your track. Even though they're your friends, find out if you should have them sign some sort of waiver. You may also need to consider trespassers, especially if your track is located away from your house, which will make it more difficult to monitor. If someone rides on your track and gets hurt, you may say it was his own fault because he didn't have permission to be there, but someone else may say it's your fault for not securing the perimeter of the track properly. Putting up a fence may be necessary, but adds to the cost of the project so factor in the extra outlay.
Drainage: Proper drainage is very important. Water is going to seek the lowest point and will take the path of least resistance to get there, possibly causing erosion ruts in the process, especially on hilly terrain. It's a good idea to do a bit of research on drainage and erosion control beforehand so you can figure out how to allow the water to get where it needs to go without taking your expensive dirt with it and ruining your track every time it rains. It may be necessary to add sections of drainage pipe in some areas, but any buried pipe needs to be covered with a good amount of dirt because drainage pipe isn't designed to have dirt bikes landing on it, and it will get punctured or crushed if its not sufficiently buffered by dirt. Drainage pipe is also slippery (even when dry) which can cause the back wheel to wash out.
Keep It Simple: Don't get carried away in the beginning. A couple of single jumps and a whoops section will be plenty. Don't make the jump ramps too steep, and don't use the whoops spacing from the pro tracks - those guys are riding pro bikes and their suspensions are set up differently (not to mention they have a ton of experience). Try to keep the whoops in a straight part of the track, not near a turn (unless you have some experience), and three or four whoops is a good number to build until you figure out the proper height and distance. If you make eight or nine whoops and find out the spacing is wrong, you've spent all that time and energy to build the whoops and now need to spend the time and energy to change them. You could have spent that time riding. Start with a whoops spacing of around eight feet, and a height of about two feet, and take it from there.
Put your design on paper This step isn't necessary, but every bit of planning helps, and many great projects started out as scribbles on a piece of scrap paper. It doesn't have to be fancy or drawn to scale but if you're stuck, seeing it in black and white may show the problem area. It also allows you to get input from friends who may see potential problems that you might have missed. You can also use a 3D graphics programs to make a mockup if you're computer-savvy. Having a basic drawing also makes it easier to do the math and estimate the cost of the track. (The MX track design pictured is Spring Creek MX track which is a pro track, not a backyard track.)
Dirt: To keep costs down, try to work with the natural terrain. If you have a totally flat expanse of land and need to bring in dirt, price it out ahead of time as it's fairly expensive. Be sure to ask if delivery is included in the quoted price. Go for screened dirt. Buying unscreened "fill" dirt might save you a few dollars, but you'll pay for it in the end with the expense and aggravation of punctured tires when your dirt bike lands on the submerged pieces of block, wood and metal. Buried debris can also increase the possiblity of an accident. If you're going with the wheelbarrow and five-gallon pail route to move the dirt, unscreened dirt is a lot harder to shovel and doesn't fit well in five-gallon pails like plain dirt does. Most tracks are built at the back of the house so make sure there is access for the dump truck to get as close as possible to the track area to keep manual labor to a minimum. If he has to drive across the lawn, find out where your septic tank, well, and leach fields are. Clay soil holds its shape better than sandy soil, but sandy soil drains better. Loamy soil is the best choice for a dirt bike track, but it's also the most expensive.
Call before you dig: If you have a large enough parcel and decide to dig a pond in order to get the dirt for the jumps, it might be a good idea to check for buried utilities. Even if there are no houses where you're putting the track, there still may be a main or secondary utility transmission line underground in the area. They're usually signposted with small metal signs, but if it's a rural area the signs may have fallen off, rusted off, or been rubbed off by a deer. It's usually a free service so it's a good idea to call an underground locator hotline to make sure nothing is beneath the ground. There may be others, but here's a link to the Call Before You Dig website that has each state's contact info.
Think outside the circle: You may not have enough land to build a traditional motocross track, so work with what you have. The Red Bull Straight Rhythm track shows what can be done in a straight line. Granted, it's a half mile long and built for pro riders, but you can start with a few piles of dirt and add to the line as time, money, and expertise allows. As mentioned at the start, you'd be surprised how much fun you can have with just a few small piles of dirt.
Renting Machinery: Depending on the size of your track, it might be worthwhile to rent a mini-excavator for a weekend. Although it makes the job faster and easier it can also add complications, especially if you're not familiar with how to operate the machine. Have the rental guy go over the safety procedures as many times as is necessary - not just for safety's sake, but because the machine probably won't start if you don't follow the proper procedure. And forget the video of the five-year-old on YouTube that's driving a Cat D8 dozer around the yard - keep kids away from the machine. Finally - don't forget that Mother Nature doesn't care that you've finally got all your friends to come over on the weekend you reserved the machine. If she decides it's going to rain, it will, so find out if you'll need to pay for the machine even if you don't use it.
How to build a backyard track video: Here's an interesting time-lapse video of a guy building a track using a small Ford tractor: