The problem with easy-out devices is simple if one considers the circumstances.
1) The fastener failed because it could not accept the torque required to turn in the threads.
2) The, much smaller diameter, easy-out cannot possibly accept even the torque which, though insufficient, twisted the fastener off.
Easy-outs are useful for removing fasteners which have been sheared off, snapped by bending, etc. but are not applicable to torque load breakage.
Breaking an easy-out off in the broken fastener adds another dimension of problems although I have seen dozens and dozens. Drilling these is fun unless you have carbide drills so avoid the problem by considering the problem.
There are many valid techniques for removing seized and broken fasteners although nothing is quite so much fun as to cause a dispute between two cranky old machinists or techs. by asking what is the best way.
IME, it is difficult to improve on heating/welding to the broken piece as has been outlined. If someone is determined to learn how to do this work, proceed with great care and do not begin on something of value.
Buy a wrecked bike and use that as the lab rat. By the time you have successfully removed a dozen seized and broken ones, you will begin to understand why those of us who have done hundreds still don't think it is as enjoyable as a sunny afternoon in the lawn chair.
While this is not true 100% of the time, you can be quite assured that trying to remove a seized fastener by use of an easy-out will be a failed attempt leading to more heart ache.....
When you get really good at drilling out 6 mm studs, try drilling out the snapped off end of a GL1100 idle mixture screw.
Didn't think I still had it but eye balled and hand drilled one for my brother-in-law last year.
ray:A #72 drill just leaves a foil thin tube of brass.
Still have the piece around here somewhere....
The real answer is not to let them seize in the first place or at least to avoid using too much torque and snapping the stud.
A very useful technique to avoid such problems is to use a "nut cracker" or small sharp chisel and hammer to split the nut axially through two opposed flats. It is most helpful to place a heavy block against the opposite flat in order to avoid breaking the stud due to side force.
One can crack the nuts in half, remove the exhaust to make room if necessary and run a thread chaser over the threads. New nuts with never-seize and all is well. If the thread chaser or die nut won't start over the ends of the threads, a thread file and or small triangular file will do the job.
