back wheel, sprocket, brake drum etc

[wadebriggs]

where would i go about buying a back wheel that would work on a mini bike that has the 4 bolt hole pattern so that you could attach the sprocket and the brake drum?

 

[SpyGuy]

ebay.

 

[ZnsaneRyder]

http://www2.northerntool.com/tires-wheels/low-speed-pneumatic-tires-wheels/item-1335.htm

There are also others without a sprocket, and different sizes.