Whenever adding trailer wiring to a motorcycle, you will need to use a powered taillight converter. Motorcycles (or any vehicle with yellow turn signals) have the turn signals isolated from the brake lights, while most trailers use the same light bulb filament for turn and brake. A converter will take care of this. Also, a POWERED converter powers your trailer lights directly from the towing vehicle's battery, rather than overloading the towing vehicle's taillight wiring circuits. Here are a couple of examples of such a device:
http://www.reeseprod.com/content/products.aspx?lvl=3&parentid=1500&catID=1535&part=119190http://www.hopkinstowingsolutions.com/products/vehicle-wiring-connectors/power-taillight-converters/short_proof_power_converter.html
