I remember shipping my first motorcycle and riding gears from a local motorcycle trader. I began as a mere rider and plummeted to a motorbike mechanic (I don’t mind getting my hands dirty). Now, I can build a chopper frame from scratch. In a nutshell, you can make a chopper frame or get the chopper-look for your motorcycle by stretching the parts of a standard frame and giving it larger rake angles. From then on, lengthening can be done by extending the down tubes, thus moving the front wheel further away from the frame. The top tube can also stretch to extend the wishbones and bottom rails.
The following is my brief step-by-step guide on how to build a basic chopper frame:
Let us begin the project by bending the wishbone tubes to make space for the seat, then welding the wishbones together and to the backbone or top tube at one end and the bottom rails at the rear end.
The next step is to weld the backbone to the neck stem.
Bend the two bottom rails taking care to avoid kinking. The section before the first bend of the bottom rails is referred to as the downtubes. The downtubes should be welded to the neck stem while, at the rear end of the bottom rails, they are welded to the wishbone tubes.
To make the chopper frame more rigid, consider welding a center post between the backbone and one of the cross braces that connect the two bottom rails. If you want additional strength, weld a neck gusset tube to both the backbone and the bottom rails.
Once you’ve completed the metal fabrication on the frame and the forks, you can then mount or secure the various components to the chopper frame. The main components to be mounted include the engine, the rear wheel, the transmission, and the gas tank.
The engine is secured by a steel bracket, known as the Top Motor Mount, which is welded to the backbone and also by two Motor Mounting Plates that will carry the motor.
The motor is fastened to the mounting plate at three different points. These mounting plates hold a lot of weight, and my advice is to buy machined, pre-drilled models instead of fabricating cheap alternatives.
Fit the forward controls to the threaded lugs referred to as Forward Control Adaptors.
Mount the Transmission Plate and the Seat Clip, and voila! It’s a chopper.