Gas powered bike assist

The electric bike solution is unapealing. Heavy, short lived, low on performance; the system needs time (something like 50 more years). Meanwhile, a 3 wheel gas powered bike, would get me to work and back every day on little fuel and some excercise. I promise to use the gas assist only when I hit the hills or the dangerous streets. Here are some links on this topic.
In fact, most common form of batteries, lead acid, have a storage density of about 35 Watt-hours/Kilogram (more expensive batteries such as Lithium Ion, only store about 150 Watt-hours/Kilogram) while the energy stored in gasoline is 12,000 Watt-hours/Kilogram. Source.

1. http://www.chrishill.myknet.org/
2. http://www.bicycle-power.com/gas.html
3. Engine kits Mitsubishi Rear Mount 43 cc 2.2 hp friction drive Quiet.
4. Spooky Tooth Cycles - Gas & Electric powered bikes and DIY kits in Arizona. Frank marketing text.
5. Bicycle-Engines.com - Frame mounted, gas powered conversion kits. 4 cycle! Photo Videos
6. So they are cheap, big and noisy. $ 450 gets this: 49cc etc. mountain bike. No deal.