Cool, another valley local! Greetings from Chandler! I have the 66cc Skyhawk motor similar to what KC has displayed on his site installed on an old Diamondback Wildwood
It's quite a motor! The mileage I'm getting can't be beat. Right now it's well over 100 MPG, because I barely have to give it any throttle at all to go the legal limit of 20MPH. Adding the oil is no biggie either, just get yourself a 2 gallon gas can and mix it in right there. I spent about $5.00 filling up the can last weekend and still haven't used it all up yet. Still have almost a full gallon left.
You'll love it. I have an e-bike also (not quite like yours - mine's a cheapie little Aowa 48v) but the gas bike is faster, goes farther, more fun and alot cheaper to own and operate. My only complaint is (due to the model of bike and tubes I'm using) it beats me up a bit because I really FEEL every bump. But it's still a great way to get around.