This website is selling so called Whizzer bikes and Whizzer engines. It has been reported to me by associates that if you order a Whizzer engine ($800+), they actually send you a cheap Chinese made 2 stroke engine, which is commonly available for just over $100. Genuine Whizzers only have 4-stroke engines.
And you really have to wonder about a company that does not accept credit cards and accepts only checks and bank wire transfers (very risky and even ebay forbids it).
I contacted the real Whizzer company in Texas and asked them if extreme-scooters was an authorized dealer and they said definitely not and that there were many complaints against them, which you can find by Googling.
The company paid a fine of over $11,000 in the state of Georgia for deceptive business practices. Obviously, it's very difficult to shut down an operation like this because they're still in business!