Yup, that is a nasty one, I think I might have warned you about this. Here is the routine:
1) Take it to an expert, probably a machinist. It will cost. Oh well... Barring that:
2) Soak it in a good penetrating oil. WD40 is poor, PB-Blaster fair, Kroil is pretty darned good.
-- Soak it overnight, no longer. An alternate oil is 50/50 acetone and ATF. Heat the outer part up until oil smokes.
-- Work the bolt back and forth no more than the maximum rated torque. You don't want to break it.
-- You don't heat it up red hot because that ruins the temper and makes it prone to break off.
Red hot may burn the corrosion out, and a splash of cold water may shock and harden the bolt enough to remove.
Use this as a last a last resort. Experts often know just the sort of corrosion where this will work first time.
3) If that doesn't work, heat the outer part up until the oil smokes and dab the threads with paraffin wax. Try it.
4) If no-go, heat up until smokes, dab with wax, smack on bolt head with hammer to loosen corrosion. Try.
5) Repeated trys may eventually get it moving, work it slowly. The wax works better than oils in most cases.
6) If the hex head breaks off, put a nut over the stud and weld it in place. It is weaker than the original.
7) It it is into aluminum, you can use a strong alum in warm water mixture to dissolve the bolt and corrosion.
-- It has to soak for 12hrs and has to be kept warm and won't work with stainless steel.
8) If the head breaks off next to the surface, you are in trouble.
--a) Prick punch the EXACT center center of the broken bolt. Grind it flat if you have to.
--b) Drill a small hole in the EXACT center of the broken bolt. Drill it right through.
--c) this may be a good time to try the alum trick.
--d) The best extractors are the fine straight spline and nut type:
http://www.parts-recycling.com/Meta...r-/Blue-point-no-1020-screw-extractor-set.htm
9) if all else fails, drill the bolt until you touch the threads (tap drill size),
-- try the oil and heat and see if you can work the threads out.
10) If all else fails, drill it out for a helicoil, or the next size larger bolt (if there is room) and tap it.
Can be a nightmare eh?
The preventative measure is drilling a small drain hole in the lower corner of the swingarm and using antiseize compound on the bolt in the future.