What are you trying to install? Trace the "ground" wire for the battery and use the same "earth" location. You really aren't limited for ground locations on the bike as long as it's not insulated by plastic or paint etc. Do have an ohm meter or test light?
The best chassis GND would be the Neg side of the battery.
pretty much any bolt that screws tightly into the frame or the motor could be a suitable GND.
Under the gas tank on the top frame rail is a bracket that holds down some relays. I used that bolt to GND some of my accessory lighting.
A forum community dedicated to Triumph Motorcycle owners and enthusiasts. Come join the discussion about performance, racing, cafe racers, bobbers, riding, modifications, troubleshooting, maintenance, and more!