by 124 » Mon Nov 26, 2007 5:57 am
Got a Dremel? Try using a cutoff to cut a slot in the screw. Use a new slotted screwdriver.
or
A screw-extractor.
or
If the cap gets messed up and you have to buy a new one anyway, you can grind the head of the screw off and twist the remaining threads out of the master cylinder with pliers/vise-grips.
Suggestions not in any particular order...

70' Honda CT70 (Trail 70; Gold)
16' KX450
16' KX85
12' YZ125