Cycle cars are machines built from bicycle and motor cycle parts and usually had small engines but the Bedelia cycle cars had larger engines up to 1200 cc. The micro car market are cars usually only had 1000cc engines and were specifically a car. From here you entered the car market with any size engine.
Scootacars were originally used as fair ground rides and were then made for the roads.
Now cyclekarts are home grown hand made cars with the unwritten rule of about 200cc and made to look like a cycle car or of something larger made small. There is no rules just have fun and enjoy one's self, The other rule is no one gets hurt.
Go karts are specifically for racing and there is two types dirt and on road. There is some new classifications streamlined and gearbox jobs. as well.
Then there is dune buggy's which are specifically driven on sand and dirt roads elaborate ones are road registered.
Mopeds were vehicles with two or three wheels with and engine size of up to 50cc and power output of only 200 watts which are legally driven on roads with out a license or insurance.
There are some who would like to ban these as there has been some deaths on the roads in NSW Australia in recent weeks. These were driven by youngsters at night with out lights or safety helmets or the permission of there parents.
I hope this my clarify things in some peoples minds.
I forgot to add in the 1/4 midgets which were raced on speedway tracks and had motor bike engines usually 500cc and they ran like a scalded cat. Some photos can be seen here.http://www.jalopyjournal.com/forum/showthread.php?t=210638
I have edited this as I was proved wrong so I hope the revised information helps.