Re: New Member
Brandon, welcome to the community. You've found the right pace to help you enjoy the hobby of motorized bicycles. There is a world of information here posted by experienced builders who will be here to offer advice when you need it.
Ball park price, $200. and up. That would be for a Chinese 2 stroke engine kit and a bicycle to install it on. You can go mild to wild but start small, get some experience and then consider upgrades. Master the basics first and get familar with the engine and kit parts.
There are also 4 stroke (cycle) engines and kits. They are typically a little more expensive and many times a second or third build but there are a few who begin with 4 strokes. Your choice.
There really isn't a transmission in the pure sense. There is a clutch which disengages the engine from the drive chain, most are manual but there are centrifugal clutches that engage according to engine speed. You will also have the option of installing an aftermarket 'shift kit' which allows use of the bicycle gears, if equipped. My suggestion would be to forego that option until you're more experienced.
We urge new members to make use of our search feature using key word/s that will take you to pages of discussion on every aspect of building and maintaining a motorized bike.
Good luck, have fun and ride safe.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"