Well this is my first instructable so lets get started. Ever since i was very young, I have wanted a dirtbike. Only problem is that we live in a suburban area and my parents arent willing to drive me to the local mx track. I am only 13, so I cant drive myself. This means I had to throw the idea of a consumer dirtbike out the window. I would have to make one from scrach. The power boost for me was from 1/2 horsepower to 4 horsepower
Step 1: Finding a Frame
If you dont already own a razor mx500 or 650, know that any 36v-size kids electric dirtbike will do. If you do not posses one, you will need to find one. Craigslist is a good place to look. I found mine for 40$, that included the frame and the wheels.
Step 2: Parts
If you have a full frame, and wheels that hold air, this is what you need:
New brake levers
Some scrap metal
Motorized bike kit, can find on ebay for 100 dollars
New rear shock
5/8 inch pillow block bearings x2
9 inch 5/8 inch keyed shaft
2 of the appropriate sized sprockets
Assorted nuts and bolts
I use my 3d printer for some things, but it is not really nessasary.
Step 3: Making the Motor Mount
The motor mount is important, it will allow the motor to mount to the frame. It is made from some scap flat stock and some 1 1/4 inch pipe i got off the end of an old electric scooter.
You will need a welder for this, so use your own or ask a freind. This is the only part that needs welding.
The pipes will need to be joined at and angle, so if you dont have the proper tools to do this, you will need to use this website: http://dogfeatherdesign.com/ttn_js/
On this website you enter the pipes diameter and what angle you want the cut and it will generate a paper template that you wrap around the pipe and cut along the line.
The angle between pipes needs to be 70 degrees. So, one pipe needs to pe perpendicular to the flat stock, and one needs to be at a 20 degree angle in respect to the flat stock. Follow the examples of the pictures and you will end up with a motor mount that mimicks the seat post and down tube of a bicycle that the motor is designed to mount to.
After you finish welding, drill 2 holes and bolt the mount to the frame.
Step 4: Exaust Pipe Bending
The next step is bending the exaust so it will fit the frame. The best way to do this is with a blow torch. Fit the engine and exaust on the frame and you will see where you need to bend it
Step 5: Adding Bearings and Rear Brake
To add the bearings, simply line them up and bolt them to the swing arm like seen in the photo. To make the rear foot brake, cut a peice of and old bike handlebar about 4 inches long. Flaten an inch of one end. Then put the flat end in the vice and bend the pie about 40 degrees. Then drill a hole in the flat end and bolt it to the foot rest bar like seen in the picture. Then, get a brake lever and drill a hole in the end of the lever so that you can bolt a peice of scrap metal to it to form a pedal. Then run the brake line from the brake lever to the rear caliper.
Step 6: Drive Train
To make the motor turn the wheel you need a drive train. Run chain from the motor to the sprocket on the keyed shaft. Add the key to the sprocket to keep it from moving. Then run chain from the second sprocket to the wheel. Your motor will now drive the wheel. To start the motor, hold in the clutch, and roll down your driveway or a hill until you pock up some speed. Then let the clich out and motor will start.
Step 7: Decoration
Im sure you will want your bike to look nice. For me that means a white paint job and blue fenders. If your are going to spray paint, you must strip the original paint off first.