You could use the lever to pull the roller off of the tire and ride it like a bicycle (very boring and slow). For more fun, push the lever forward and lock it in place, then push the decompression lever and start pedaling. After a few pedals, let go of the decompression lever and it should start right up. Give it gas with the hand throttle!
I can't remember if it would idle while stopped. If it did, that means there was a centrifugal clutch of some kind. I think it would, but I am not sure. If there was a centrifugal clutch, how would it pedal start?
I don't think we hardly ever used the lever to pull the roller off of the front wheel.
The Solex was a very reliable moped that could be used for commuting. It took a lot of rough handling at our house and kept on running.
We used to run it in wet weather and through mud and it slowed it down, but if you grab the lever and push it forward it got better traction.