I'm trying to take off the shifter to repair it, but the head of one of the screws is stripped. I've drilled a hole into the screw and have tried to use a screw extractor but it won't budge at all. The screw seems to frozen in there. The other screw came off without a problem. And with the head of the screw not being exposed, I can't cut slits into it to try to make a phillips fit or to use a chisel. Any suggestions would be greatly appreciated.

Thanks

If you haven't totally killed the screw already try a small tap wrench, plus soak it in WD40 overnight. That'll shift anything. If the screw is totally, erm! screwed, then you'll probably have to drill it out completely.
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MC28 SE -sold-
MC21 with RS250 engine -for sale-
MC21 race bike -soon for sale-

You could try heating the area up with a blow torch, the frame area should expand quicker than the steel bolt, which should make the removal of the broken bolt easier. I used this method on a project of mine several weeks ago and I managed to extract the "frozen" allen bolt.
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Hmmmmm!

you can also use a hot air gun(the type used for paint stripping)it will get just as hot as a blow tourch and wont set fire to anything,remember it still gets hot,ie it will still melt plastic parts.