For our last vehicle, we will mainly use our pencil and black marker. You will color it at the end, and can choose ANY colors you want!
Start by drawing 4 circles: 3 in a row (with some space in between) and then one on top of the right circle.
In the right circle, start by drawing a small circle in the middle. Then create a thin rectangle coming out of it. Angle it as if it was a hand on a clock pointing somewhere between 10 and 11.
Create a second rectangle, slightly wider, but just as long, on top of your previous one.
Make another rectangle of the same width, but slightly shorter, on top of the previous one. Make 2 lines and fill in the "ends" of it.
From here you can draw your handle bar. We'll only draw one side, which kind of looks like a short hose coming out the top.
Draw a curved rectangle type shape to the right of your top and bottom "ends" from before.
Below the bottom "end", draw a large moon shape that is a little wider than your right circle.
You can now trace your circle, while making a small "donut" around your center.
Draw another circle around the edge of the big one to complete your tire. Then draw 4 lines coming out the left side of your tubes, with a curve on the left edge.
Draw a wavy shape that reach around the middle of your left circle. Make sure it dips down in the middle (above your center circle).
On the bottom side, make a hook shape that goes around the center of your middle circle.
Finish of the left side with 3 lines or so. 
From the bottom of your center shape, create a large arm shape that reaches the center of your left circle, and then draw a small circle.
Trace your left circle, and then make another to finish your tire. This one can look thicker than your front tire.
Draw 4 small lines, where 2 of them almost look like 1 line that had its middle chopped out.
Then draw a bunch of small, squished ovals. They kind of look like rice!
Fill in the "arm" with a couple rectangles and triangles.
To finish off the tires, draw 5 lines. Almost like a stick figure with his arms up.
Then draw 2 more lines, one on the left, the other on the right, of each of your last 5 lines.
Fill in any remaining space with more lines, and add some shapes inside the center circle.
Do the same for the front tire.
Go ahead and erase all your pencil circles now.
Add in a seat in the middle of your center shape.
At this point, you can fill in the center shape however you want! I added some lines near the top and weird shapes along the bottom side.
Now we can start coloring. First, let's knock out the tires with a black or dark gray.
For my dirt bike, I decided to use red for my main parts.
Then I used blue for a lot of the smaller parts!
Add some shadow along the bottom with your pencil, sign it, and your dirt bike is complete! 🎉