I had a problem with my voltage regulator a while back. it degraded to little over 4 volts, dimming the system way down.
While your cleaning your grounds, disconnect the voltage regulator and start the sled. If the lights are brighter then you have found your problem!
NOTE: don't rev it too much (over 2300 rpm). You could over voltage the system and it could blow all of your lights.
1997 Yamaha Vmax XTC ER
1979 Yamaha Exciter 440
1997 Yamaha GP 1200 Triple
1967 Mercury Cougar XR7
2015 Season Mileage:58