Ability to Switch Gearing
Mini Bike Transmission Rack
The design uses a swing arm that connects to the jack shafts between the engine and the rear wheel. This arm allows you to change the gearing on the step pulley. The spring keeps the arm taught, so your belt doesn't slip off.
The transmission rack consists of two channel uprights with bearing housings welded at both ends. These housings are merely short lengths of pipe with an inside diameter that will provide a snug fit for the bearings you use.
The two uprights are welded to opposite ends of a pipe brace; the jack shafts are slipped through the bearings and held fast with retaining collars. This entire assembly is mounted in the frame by means of simple mechanical pivots.
The lower bearing housings protrude into holes in the support plates at each side. The pivoting feature permits adjustment to keep the drive belt taut. The rack is tensioned against the belt by means of a spring hooked between two flat-iron brackets.
The front bracket is drilled to slip over a pin projecting from the top of the rack. The rear bracket is bolted to the frame.
Whether you add a screen (or shroud) around the transmission depends on the use (or abuse) you'll give the scooter.