I'm fairly new to RC bikes but I know how the full size ones work very well. There are two ways that RC motorcycles turn. Kyosho uses a kind of odd ball way to turn their bikes and I can't think of a way to explain it so I'll let someone else try . I know thunder tiger and the new venom gpv-1 use the "normal" way to steer a motorcycle. With any bike or motorcycle the front wheel has to turn right for the vehicle to turn left (yes, the opposite way that you want to turn). What this does is drives the front tire out from under the bike and naturally leans the bike into the corner. After the bike is leaned into the corner pressure needs to be released from the handlebars and the front tire finds its own position to maintain the lean angle that it was left at. If you push the handlebars further right in a left corner the bike will lean lower to the left. If you push the handlebars left in a left corner the motorcycle will stand back up. A motorcycle gets its turning radius from its lean angle, not from how far the front tire is turned (unless you're at low speeds like in a parking lot).

Those are the basics of how a motorcycle turns but when it comes to the speed at which it can corner and how tight it can corner there are a lot of other variables which takes a lot of explaining to understand how it works.