7 Things You Want in a Street Legal Dirt Bike (And 4 You Don't)

All motorcycles are awesome in their own ways. What you choose to ride is much less important than the fact that you ride at all. However, in the realm of converting dirt bikes to street-legal machines, all bikes are not created equal. Some will inevitably be more of a chore to convert than others.

That’s just the nature of the game.

To get an idea of the issues involved in making a dirt bike street legal, let’s look at some of the included equipment that makes a certain dirt bike an excellent choice for a street-legal conversion. Then, we’ll point out a few things that are best avoided.

Again, it isn’t a question of whether a bike can be made street legal, but rather an issue of whether or not it is worth the expense and effort required to do the job right. And in our humble opinions, it absolutely is.

2013 Yamaha WR450F Built By Dirt Legal

Which Features Make the Perfect Street Legal Dirt Bike? 

Some bikes come from the factory with much of the required equipment for a street-legal conversion, while others force you to do a lot more wrench turning.

A prime example of a great street legal dirt bike is the Yamaha WR450F, though it’s far from the only good option. Here are a few of the reasons that bikes like the WR are great dirt bikes for the streets.

Four-Stroke Engine

There was a time when the 2-stroke engine was ubiquitous among dirt bikes, but those days are long gone. Still, it is relatively easy to find used 2-stroke dirt bikes for sale at bargain prices.

These bikes are no bargain on the highway, though. The WR450F’s 4-stroke power plant is thoroughly modern. It has dual-overhead cams and four titanium valves, so maintenance is a fraction of what it is on the antiquated but fun 2-stroke engines. 

Wide-Ratio Gearbox

The WR comes with a torquey 5-speed transmission which has wider-than-normal gearing for a dirt bike. It pulls hard down low, perfect for getting off the line at stoplights and up ahead of dangerous traffic conditions. The wide gearing eases riding in technical off-road sections as well, as it reduces the need for constant shifting to stay in the power band. It is likewise perfect for urban environment to boot.

Factory Headlight and Taillight

The factory-installed headlight and taillight of the Yamaha WR450F are more than just a convenient addition. They take much of the headache out of a street legal dirt bike conversion. Because there is already a wiring harness, tying in turn signals is a much simpler task. The benefits of having these factory-installed items on a dirt bike cannot be overstated.

Battery and Generator

Driving the factory lighting package on a WR450F are a high-capacity generator and 12-volt battery. Both are capable of pushing add-ons like turn signals with ease. There is no main switch or key, so theft prevention is an issue that you must take into account when converting a street legal dirt bike.

But, that is a much better problem to have than the myriad headaches that arise when upgrading or installing an electrical system on a dirt bike that was never meant to accommodate one.

Electric Start (With Kickstarter)

That beefy electrical system also powers another hot commodity.

A kickstarter on a motorcycle is a nice thing to have when the battery gets drained, whether from disuse or from forgetting the ignition in the “ON” position (not an issue on the WR). But there’s no arguing that electric start is a lifesaver.

Cold starts are no longer something to dread, and stalling off the line doesn’t leave you at the mercy of impatient motorists. Simply find neutral or pull in the clutch, press the start button, and you’re back up and running – and out of harm’s way.

So, you might as well have both.


Newer WR450F models come equipped with a large-capacity radiator. Additionally, they have an electric fan to help with cooling when everything comes to halt on the road. Without the luxury of a radiator, a rider must begin counting down as soon as the bike has to sit motionless while running.

In the heat of summer, overheating can occur within the time it takes for a traffic light to turn green. Liquid cooling eliminates this concern altogether, and it’s a no-brainer on a street legal dirt bike.

Enduro Tuning

The gearbox and engine on the WR are tuned for fast-paced trail riding, rather than the sudden acceleration required of motocross bikes. This means the WR is highly capable even at freeway speeds. Riders accustomed to modern street bikes may find themselves toeing for a sixth gear at higher speeds, but the WR is more at home at high speeds than the average dirt bike could ever be.

What to Avoid in a Street Legal Dirt Bike

We’ve talked a little about how the Yamaha WR450F is our favorite street legal dirt bike, and we’ve supported that claim with cold hard facts. Now let’s see which bullets you’re dodging by choosing a dirt bike with all the right features instead of all the wrong ones.

Two-Stroke Engines

The classic 2-stroke dirt bike elicits dreamy looks from those who prefer its snappy power band, but it also brings with it a headache that never goes away.

Because oil must be mixed with the fuel, operating a 2-stroke on the road means traveling with bottles of oil everywhere you go. It’s not like they sell 2-stroke oil at every convenience store, after all.

Also, 2-stroke engines typically have short service intervals, and they require top-end rebuilds much sooner than 4-stroke engines normally do.

That’s not to say you should never make a two-stroke street legal. It’s just the difference between a high-maintenance supermodel and a dependable daily companion with grease under its fingernails.

Small Displacements

A 200cc thumper can be a hoot on a trail, but its lack of top-end potential puts its rider at peril when it is made street legal.

Their lightness means these small-displacement dirt bikes have plenty of pep, and they get off the line enthusiastically. But, their acceleration flat-lines at much slower speeds than most other vehicles on the road are capable of. On the street, riders on these bikes may find themselves impeding traffic on the highway, and that is not somewhere you want to be.

Air Cooling

A lack of liquid cooling is no real issue for a dirt bike on a trail, but once you’re in the urban environment, staying cool becomes a serious issue. It takes only one stagnant traffic jam for the problem to arise.

Sitting still for too long on an air-cooled bike is an obvious recipe for overheating. The only option is often lane splitting, which is a no-no unless you live in California.

Kick Start Only

A lack of electric starting on a dirt bike isn’t just a problem when you stall out in traffic.

It is a tell-tale signal that there is going to be a lack of available electricity for powering the necessary lighting to convert that dirt bike for road use. Headlight, taillight, turn signals and horn will all draw off generator, which will inevitably be a much smaller capacity on a kick-start only dirt bike.

Choose Your Dirt Bike Wisely

For these reasons and many more, the Yamaha WR450F is a much simpler conversion option than some others, but it isn’t the only choice.

The Honda CRF450X is another example where the manufacturer already did much of the dirty work. Even its little brother, the CRF250X, can make a fine option depending on what you’re going to ask of it.

Many KTM dirt bikes are likewise well-equipped, and these Austrian 2-strokes typically come with high-power stators and a full set of lights.

Many factors conspire to complicate a street legal dirt bike conversion. The limiting factors of your choices depend greatly on your budget and your mechanical abilities. When money is tight and time is not a factor, the more mechanically inclined may consider it worth the trouble to convert a bare-bones dirt bike for street use.

For the rest of us, the more of the required parts for conversion that the factory takes care of, the better.

ktm legal.jpg

Have a dirt bike you want to make street legal?

That’s where Dirt Legal comes in. Making things street legal is what we do. Just call us at 800-994-7513 or email us at info@dirtlegal.com. Or visit our Dirt Bike Conversions page by clicking the link.

From there, we’ll send you some documents to fill out. We work with the DMV to ensure that all laws are followed in making your dirt bike street legal to drive on public roads. You’ll get a license plate, title, and registration!

Just add your state’s required legal parts – blinkers, headlight, and so forth – and you’ll be legal. No hoops and no hidden clauses. Just you, your street legal dirt bike, and the open road.

If you have a dirt bike that's not street legal, what are you waiting for? Make it street legal today.