Re: New to building / motorized bikes
Sorry to be a downer. But I think you're being over-ambitious. Unless I'm misunderstanding your questions, I don't think you've got the knowledge to actually build a bicycle of your own. You need to keep your safety in mind. And designing a bike requires a lot of knowledge of stress points, etc. Plus the fact that it'll be expensive and take up an awful lot of your time.
Here's my advice. Get a Huffy beach cruiser from a big box store. (I'm recommending Huffy because they're stronger than people think. But there's other brands.) Plus get a $180 2 cycle engine/direct chain drive kit. Put the two together and start riding. (It's not really quite as simple as that. There's small mods and adjustments needed. You can learn about them here.)
It's quick and it's cheap.
Best of luck to you.