trailer lights

imported post

On the bike you may be looking at some added on wiring.
The bike wire colors should be:
Left turn: Orange
Right turn: Light blue
Tail lights: Brown
Brake Lights: Green with Yellow tracer
Ground: Green
Same colors for your GL 1200, pretty well standard for Honda harness wiring.
Your bike has separate wiring for the Brake Lights and Turn Signals. The trailer more than likely uses the same bulb filament for the turn and brake. If so, You will need a converter to wire the trailer to match the bike wiring. Auto parts stores or U-Haul have them.

imported post

Here's what I use on my 1100.

Negative Input Short Proof Power Converter Part#: 46345

http://www.hopkinstowingsolutions.com/products/basic_wiring/taillight_converters/power_converters/negative_input_short_proof_power_converter.html

• For vehicles equipped with independent bulb turn signals or common bulb systems
• Negative input converter for Ford Windstar 1999-03 and Lincoln LS 1999-06
• Powers up to 8.0 amps per output
• Receives power directly from the battery
• Protects tow vehicle electronics and itself from wiring shorts, Self- Resetting
• Double-Molded Weatherproof Design
• Provides for brighter bulbs.
• Includes: 12 ga. power lead wire, fuse & fuse assembly, splices, and ny-ties

Got it at Northern Tools. Cost around 50 bucks? Well worth it as it isolates the bikes electrical system from shorts in the trailer wiring.