This one was built from a 20" suspension bike and a 49cc pocket bike engine. It was geared to go about 20 mph maximum. I was going to use it for riding around in the woods too. It had no-flat tires on it and was pretty comfortable to ride.
In my plan picture below you can see that it was going to have pedals also but I didn't get that far before someone offered to buy it. The frame was a bit short for my height though. I should have stretched it a few more inches when building it.
These pictures were from before it got all the lights and controls mounted.