I want to do a guide on how to buy and look out for dodgy pocket bikes. They range in prices from as low as $200 for a Chinese 37cc to $6000 for a Euro 49cc. I will start with the low priced first as there are more of them on Ebay.

The difference between a cheaper and a more expensive bike is the quality of the bike overall. This include welding of the frame, nuts and bolts, how well the engine had been put together, etc. These bikes are "copies" or "replicas" of some Euro bikes. They are made in China and the quality control is not perfect.

There are Air-Cooled and Liqud-Cooled. Air-cooled are slower than liquide-cooled, it doesn't matter how much you spend upgrading the engine, it will still have a hard time keeping up with the liquid-cooled. So if you have the money, buy a liquid-cooled.

Don't be fooled by sellers claiming their bike can do 120km, the world record for a pocket bike was set in US at 60 mph (or something like that). Air-cooled engines in stock form can do 40km/h, liquide-cooled can go up to 80 km/h stock. Some of the bigger sized bike comes with a speedo, they are very inaccurate and will show double the speed of what you are actually doing.

Things can go wrong and will happen more often with a low priced bike. Engine can blow up, wheels falling off, etc. It is not hard to fix, but it will be very frustrating. Believe me, I've been there.

The reason why a person would buy a more expensive bike is mostly the speed of the engine. CAGs is about 3hp, while an Euro will have upto 15hp.

There are some bike from China that is very good, and can keep up with a Euro. Banshee is 10hp, Z1 is 12hp.

Search google under pocket bike forums, and you will find very helpful tips.