I believe you'll want to access the speedo cable plug-in from the front of the bike. Remove windshield and garnish strip, maybe headlights and their bracket, the vent under the headlights, etc. and you'll be able to access the back/bottom of the LED instrument cluster.
"During times of universal deceit, telling the truth becomes a revolutionary act." ~ George Orwell
1995 1500 Aspencade named "Cochise"
1985 1200 Aspencade named "Tatanka"
IDMWT club #18