hi, it happens to big twins as well, clean & check the splines  for wear as you don't know how long its been loose for  ,    it should not have excess up & down play to much   they are loose fit new on the milti spline new  but not excess  if its worn not to bad i use  loctite quick metal on the shaft & in on the pulley, must be very clean 1st put on & off 2 times to check that no snot is were its not wanted like inside the pulley spacer etc ,  do belt up so as just before firm , use 620 loctite snot on main nut it it holds better at higher temp, the socket size is 1 7/8  it's the same nut as big twins 90 up .

i forgot to mension i use a small rattle gun  nothing too big  because most stock speck  can come loose again  after time  esp if the pulley is a bit worn on its spline ,      ive done about 40 this way never had  1 come back ,     touch woody

hi, i have cut my scocket in 1/2 & extended it 5" so it fits the big twins as well  if your scocket is not long enough its easy to cut it on a lathe & extend & weld it so it reaches over the output shaft  , i put a texta mark on the scocket so when i do it up i can see when its tight & not going any further , let  it settle for 10 min & check it again i always double check eveything being the last person to work on it if i don't check it  whows  going to ,  good luck with the sporty