Hmm. I sense "magic pill" syndrome here. Are you feeling lack of motivation about riding a bike, or about weight loss? They aren't the same.
I was motivated to lose weight because of my health and because once I started I felt good about it.
I was motivated to ride a bike because I didn't know how and it looked like fun. Weight loss, thank God, was never a motivation for me. (I'd lost 125 pounds before I learned to ride.)