Re: complete newbie to motored bicycles
To start - don't expect 120 MPG. Myself, I get around 65 - 70. I could get this up to 80 - 90 were I to 100% of the time be pedaling along side the motor, but on a 40 mile trip that is unreasonable - though understandable.
Based on the season, you might want to wait until winter to get your first motor - most online retailers lower the prices in the off season to increase winter sales.
For other retailers, I would recommend you check out the sponsors on the left and right sides of this forum (you'll notice MotoVelo is not one of them).
As far as a brand name of motor, I always recommend Raw brand motors, as they have a great reputation which I can attest to through my own personal experience.
As far as laws, I suggest you use the search function at the top of the page. There are MANY Cali riders on this forum, and it's a topic on which I'm sure has been thoroughly hashed over.
The biggest tips I can offer you are these - expect to spend about 200 -300 bucks in aftermarket parts if you want a daily driver out of your motorized bike. The most common are aftermarket carburetors/modifying carburetors and intakes, and replacing the stock exhaust with any form of expansion chamber. Myself personally, I recommend immediately going with an alternate rear sprocket mounting method using the disc rotor mount on a disc brake wheel. As well, most kits will need a chain upgrade to #41 or 415/415H. A very common one is a sprocket with a smaller amount of teeth, 44T is stock, and I've heard from many people, myself included that 36T is a very good replacement, though in SF area with the hills you might want to stick to the 44T. Hardware upgrades are most definitely in order, as all of the stock hardware is aluminum allthread stud bolts. You can get much of this from your local hardware store. Replacing the stock sparkplug with an aftermarket NGK plug that you select based on your climate is also crucial to proper operation. The last important upgrade is a dual pull brake lever, so that you can eliminate the left front brake lever and use both front and rear brakes off of the right lever. Maintaining brake pads is a major pain, as slowing from speeds of 30+ through the city is very taxing on them.
There are more things than this, those are the most crucial that come to mind at this moment. These are RIDE ONCE, TUNE TWICE kits - never forget that.
Welcome to MotorBicycling.com Ben.