Re: first build!
They called those straight tube framed bikes "Lightweights" when I was kid. It looks good motorized. The skinny wheels should be OK with a stock motor if you maintain them. I ran a 26x1 3/8" wheel on the back of my motorbike for a while. If you hop up the motor, you will probably need a tougher back wheel.
“You're only young once, but you can be immature as long as you like" -Unknown