Have you looked into gas powered motors for bicycles?

I purchased mine, a 66cc engine from gasbike.net

In 2010 I took a 207 day, 10,000 mile trip double-crossing the US that started with a 2-cycle engine on an old 26-incher.

I managed about 4,000 miles from the engine - with a BIG smile across my face.

Engine-wise: 'complete' kit delivered to the door for about $150 and installed in long day. Fairly quite - I often listened to my portable radio carried in my shirt pocket. Reception in remote areas was more of an issue than the noise interference. 120 miles per gallon of fuel - carried a one-gallon fuel can to mix oil. Easy start - get to riding speed and drop the clutch to start - no shifting, just go - slick, motorbike-type hand throttle. Powerful enough to carry me (200#) and pull my two-wheel trail loaded with 30-35# of gear as fast as 22 mph (across Florida and up the east coast to Virginia where I turned west on the Trans-AM. Base cruising speed was about 15mph because I wanted the engine to last. Motor was 1) tired after crossing Montana going into the wind 2) didn't like 4,000+ altitude. Do some homework and carry a different needle for the carburetor when you get up to the high country - upper west US.

Bike-wise: It will go through rear tires and chains. I bought slightly heavier $10 chains from real bicycle shops but normal junk chains work; I bought my tires at Wal-mart for $20-ish and managed about 600 miles per tire.

Trip-wise: when you get near St Louis MO, turn north and catch AdventureCycling's Lewis & Clark Route - more stuff to see. I rode on the TA, L&C, Northern Tier, Cascades, Western Express, Grand Canyon, Southern Tier, and Mississippi Natchez Trace - L&C was truly enjoyed; because it had many L&C rode-side tourist stops.

Map-wise: get a gps and download AC's data - but the maps had info about free stops. I didn't have the maps but I stopped for free everywhere - I stayed indoors 3 days of the 207! I even stopped/tented in/near Wal-mart parking lots.

Legal-wise: Not so much, but you can trust that, unless you are being stupid, you will never be hassled. Well, other than the many many questions that will come e-v-e-r-y-t-i-m-e you stop for fuel.

Good riding --- and afterwards, come to Alabama to paddle our 631 mile Scenic River Trail - way more fun than biking because you can carry everything you want in big kayak or canoe.

Warren
findingwarren.com
AL-GA '08
GA-AL '08
ASRT '09
EDC 10,000 '10
FCT '11-12
GDMBR '13