Of all the various forms your bike can take, a full-blown freestyle machine is quite possibly the simplest in terms of modifications, maintenance and execution. Your best bet is to begin with a light, powerful 250cc two-stroke (although thumpers are becoming more prominent in jumping circles) and then fine-tune the bike to your specific preferences. Get out that hacksaw, because here is a crash course in how to prep your bike for freestyle flight!
When you're flying through the air hanging on to the seat by your fingertips, your freestyle dirt bike's front end darn well better be straight as an arrow. A tightly cranked steering stem or-better yet-a good stabilizer will become your best friend when you leave terra firma. A damper also helps on no-handed landings, and you can even use its resistance to help bring the bike back from big, whipped-out tricks like no-footed Nac Nacs and switchblades. Just be sure to get a stabilizer like this WER that mounts down by the fender, as you'll need the extra room up by your handlebar.
Don't fuss too much about the gearing on your FMX bike. Unless you plan on riding in a super-tight stadium or jumping an outdoor football field, the stock setup will do just fine.
A properly-functioning chain is an essential component to not breaking yourself off on a ramp, which may be why many FMXers turn to aftermarket chain guides (like the plastic-made units from T.M. Designworks) to bring more protection and reliability to this oft-overlooked part.
Unlike motocross or off-road, you don't need gobs of power to be a competitive freestyler. But when you're launching 75-foot hits straight out of tight turns, a little extra hit doesn't hurt! Just bolting a pipe and silencer onto your machine can give you that little extra snap that it takes to get over an especially tricky jump. There's no need to worry about big-bore kits or expensive cylinder modifications on an FMX bike, but a few smart mods can make a noticeable difference.
If you're going to build a proper freestyle dirt bike, good suspension is key. RG3 tuned this shock to have stiffer valving and better bottoming for the harsh hit that the bike experiences when slamming into large takeoff ramps. A slightly stiffer spring isn't bad to have for poorly judged distances, but you want to be careful that you don't alter the bike's stock handling too much and turn the machine into a difficult-to-turn, unsettled platform. Do some testing to see what works for you.
As a rule, a stock fork setup is borderline inadequate for FMX applications-you can get away with running one, but something stiffer is generally better. Go in stages and try to find a setting that provides adequate bottoming resistance on jump faces with a nice, smooth rebound. Stock springs and a bit of valving should do the trick, but go stiffer if you feel the need.
Speaking of the handlebar, if you want to be a well-rounded freestyler, you're going to want to ditch that stock setup and go with something a little easier to step through. ProTaper makes a Pastrana-bend bar that boasts a whopping 121mm of height, and Easton's Freestyle bar (pictured) is right up there at 108.6mm tall so as to accommodate your feet on barhops, saran-wraps and the like. Stay clear of anything with a crossbar, as they make bar tricks a chore and are only good as a grab rail for rodeo Heel Clickers. And never, ever remove your bar pad under any circumstances!
In order to keep from snagging the throttle cable with a boot and turning a bike into an aerial chain saw, cinch the cable to the bar using a zip-tie and a small piece of fuel line. Simply stick the zip-tie through the tubing, loop it around the cable, go back through the tubing and attach to the handlebar. As long as the throttle still operates normally, this little shortcut can open up the bar area and gain you a good bit more clearance to swing boots through.
A staple mod for every freestyler is a good set of grab holes, which are the basis for over two-dozen superman seat grab-style tricks. In truth, a good grab just consists of an accessible, wide place for you to get a solid hold. Most just cut the sidepanels and airbox out using an angle grinder. On Hondas and Yamahas, subframe modifications are necessary for the best feel, and any brand of bike can benefit from the proper application of grip tape. Most skateboard shops sell grip tape for around $5 a board length; the more aggressive grits will tear up your gloves, but they obviously provide the best grip.
Obviously, cutting down your seat is a necessity when setting up your bike for ramp-hucking glory. Not only does a low-profile seat aid you in getting a solid grab on your holes, but it also gives you more room to swing your legs over, around and through the cockpit. There are many ways to cut down a seat, but the best is to remove the stock cover, use an electric turkey knife to trim off the foam you don't want and then smooth the entire operation out with a handheld belt sander. A gripper seat cover can top off the job nicely. Be sure to leave at least some foam, though, because that seat base is harder than you think!
It's not uncommon to see freestyle bikes with cut fenders, but this customary mod is essentially useless save for its decorative appeal. The only utilitarian function of cutting your plastic is to gain a few inches of clearance around the rear fender for Indian airs, and this is a luxury alteration at best. Cut your plastic as you please, but be aware that overly hacked fenders are a telltale sign of an FMX wannabe.
While you won't be crossing many logs on an FMX course, a glide plate is still a good idea. Why? Because without a good skid plate your bike's frame rails are exposed, and these can stick into a landing if you come up a few feet short. On the other hand, giving your bike's underside a smooth surface helps increase your odds of riding away from a harsh landing.