Best Dirt Bike's To Make Street Legal

The Path Well-Traveled


What to look for when you want a simple street-legal conversion.


Motorcycles are all 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, let’s look at some of the included equipment that makes a 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.


What Makes for a Perfect Street-Legal Conversion?


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 the former is the Yamaha WR450F, though it certainly not the only option. Here are a few of the reasons we feel it’s a great dirt bike for the streets.

2013 Yamaha WR450F Built By Dirt Legal


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 WR’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 it reduces the need for constant shifting to stay in the power band. It is likewise perfect for urban environments.


Factory Headlight and Taillight


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


Battery and Generator


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


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 the 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.




The new WR450F comes equipped with a large-capacity radiator. Additionally, it has an electric fan to help with cooling when everything comes to halt on the road. Without this amenity, a rider must begin counting down subliminally as soon as the bike has to sit motionless while running. In hot, summer-like conditions, overheating can occur within the time it takes for a traffic signal to cycle to green. Liquid cooling eliminates this concern.


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 a capable urban machine as well, 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 in that environment than the average dirt bike.


What to Avoid in a Street-Legal Conversion


2-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.


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 soon find themselves impeding traffic, and that is nowhere you want to be.


Air Cooling


A lack of liquid cooling is no real issue for a dirt bike on a trail, but once in the urban environment, air cooling becomes an 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 if you don’t live in California.


Kick Start Only


A lack of electric starting 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 the bike for road use. Headlight, taillight, turn signals and horn will all draw off generator, which will inevitably be small-capacity on a kick-start only dirt bike.




As we mentioned, the Yamaha WR450F is a much simpler conversion option than some others, but it isn’t the only choice. Honda’s CRF450X is another example of a dirt bike on which the manufacturer already did much of the dirty work. And, even its little brother (CRF250X) can make a fine option, depending on what you’re going to ask of it. Many KTMs are likewise well-equipped, and the Austrian maker’s 2-strokes typically come with high-power stators and 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. But, for the rest of us, the more of the required parts for conversion that the factory takes care of, the better.


Do you already have a dirt bike that you'd like to make street legal?