It spins on the crankshaft.
When the bolts come loose it sounds like a big end bearing has failed.
Usually the smooth rotor part on the big reduction gear gets munched up, far more common than the loose bolts
(I specialised in these things for 3 yrs)
Pull the left cover, Check the 3 bolts, if any are loose remove them and check for wear. If not, remove centre bolt holding ATD and slide big gear off crank end. ( its splined on, no tapers)
Remove starter clutch and you'll probably see indentations. ( the rollers may fall out, best to remove as a unit and lay it flat, gear up)
PJ