JWR,
I discovered motorized bicycles last year after going from and $80,000 annual income a year to zero.
I first saw a kid riding one in Los Angeles and asked him where he got it and the details. Turned out that a distributor of these kits was located up the street from me. After much research and trial and error, I found a Diamondback beach cruiser full size bike from Dicks sporting goods with a front fork that had a gas shock, for less than $200 on sale.
I then purchased a kit online and followed the instructions. Needless to say it didn’t work right away.
After more reading on the troubleshooting section in the forum I upgraded to better chain, upgraded rear wheel and axle due to alignment issues and had a proper motor mount fabricated with rubber washers to reduce the vibration.
The result was a bike that I rode all over Indianapolis Indiana last fall.
I discovered that in Indiana, under 50 cc engines do not need a license to ride on the road. Downside was the 25 mph speed limit on these machines. My kit was 66 cc; but I never had anyone check it and the police pretty much ignored me.
I even used it on the bicycle trails, since the stock motor was so quiet, I would peddle along and occasionally when I wanted a burst of speed I would just pop the clutch and give it some gas.
I avoided running high speed on the nice paved and mostly unused trails to avoid unwanted attention. When the time came to use the streets, I was able to keep up with traffic doing a estimated 30-35 mph. Most automobile drivers were unaware that my bike was motorized and would pull risky maneuvers to get around me at times; even when I was dong the speed limit.
When cold weather came in the fall, I continued to use the bike till the first snow. The engine is two stroke gas; running 87 octane unleaded, an approximately 50-to-1 gas-oil mix and a dash of Marvel Mystery Oil
All new kits come with a catalytic converter in the muffler and should not smoke much if at all.
The engine is very simple mechanically. It is started by peddling the bike to about 5-7 mph with the clutch engaged and the carb choked. Release the clutch gently to start the engine spinning. Engine will start to fire after a few seconds and run a bit rough for a few hundred yards until the engine warms up. Do not give it any throttle until then. When the engine starts running smoothly, un-choke the carburetor and gently give it gas to accelerate. When the engine is fully warmed up you can make full speed.
To stop, press the kill switch that grounds out the spark to the frame, and engage clutch.
66 cc (advertised as the 80 cc model) engines are rated at 2.8 h.p. and will go up to 3.2-3.5 h.p. after being broken in.
Typical motor bicycles get between 50-150 m.p.g. depending on load, speed, driving habits etc. I am a rather big man and weigh close to 300 pounds (nearly all muscle). This kit engine moved me along on the flats at a good speed and a afternoon of fun riding used about a half gallon of gas. If you had to travel a long distance with only pocket change expenses or if inflation made auto driving very expensive then this would be a good way to go.
These motor kits can be adapted to tricycles, recumbent bikes, and can easily propel a combined weight of rider and cargo of more than 300 pounds.
For more information, see this motorized bicycle forum. Regards, – M.B.