I remember a greenspun post where someone had to take the rotor off which was contrary to what he read in his manual (clymer??)
According to the shop manual I count 6 bolts on the upside, 21 bolts bottom side and 1 inside (Rotor side, near where the oil strainer is supposed to fit in).
So, if you have 28 bolts removed (and the PO hasn't cemented the crankcase halfs using Hylomar or something) I'd guess there's not much left what could hold it together.
The workshop manual says the rotor has to be removed (+ oilfilter, oilstrainer, oilpan, oilpump, cyl. + pistons, clutch, gearshift linkage, starter, advancer, pulser, primary shaft....guess that's all
)