Try PB Blaster (= high tech penetrating oil) on it.

This set screw design is a little famous for acquiring
stripped threads and ultimately ceasing to hold the rotor
on. Someone might have torqued it because of this concern.
Or used Lock-Tite on it.

Should you destroy the female side threads, there is a
jury-rigged solution. The alternative is to buy a new
distributor housing (having a new rotor shaft, etc.), which
ISTM one should do about mid-life for these 1990s Hondas.

<merlotbrougham@hotmail.com> wrote
> Hi all,
>
> OK. After spending a couple hours and over a hundred bucks
> doing yearly
> maintenance, I can't get the little rotor off. It's held
> on by one
> philips screw and I'm afraid I'm stripping the thing by
> trying to get
> it off. The edge of the rotor is good and straight, but a
> little
> frayed. I WANT to replace it; it's personal now. Any tips?
>
> '92 Civic EX Sedan 140k miles
>