92 softail HC, 19k miles, new tires full service and new rider. 55 mph no issue, 60 mph, right floor board starts vibrating significantly, left side normal, pull clutch, reduce throttle, vibration stops. Checked under floor board to make sure exhaust not touching and it appears clear. Any suggestions would be great.

 

Tighten up everything. If everything is tight, loosen / remove and reinstall.

Make sure no other parts are touching the floorboard.

Check the condition of the rubber inserts. If it is hard, replace them. When they get old, they get hard and no longer absorb vibrations. I ordered replacements from Surdyke.

 

As Prot suggests. I replaced my rubber doughnuts on my floor-boards a while ago, having discovered a few had split and sheared. Sometimes little things can cause what seem like big problems.

 

^^^This^^^

 

Yup, what everybody else said. New footboard mats (the rubber isolators are part of the footboard mat). I consider these a "wear" item and replace them every few years because the rubber "balloons" under the heel of the board break down. Part number 50614-06 for the new style "ribbed" footboard mats.