Motorcycle Repair: Honda 900 Cutom exhaust port stud, honda 900, aluminum head

Question
My 1982 Honda 900 Custom with 34000 miles has an exhaust stud that broke off on one of the inner exhaust ports about 1/16" below the casting.  Are these studs threaded or cast in place?  If threaded I plan to pull a good stud to find out how deep it goes into the casting before drilling.  If cast in place I figure to drill and tap to install a stud.  The engine is still installed. Thanks for any help you can provide.  Ray

Answer
The studs thread into the head about 2.5 diameters or 19-20 mm.  The best way is to try and drill them out.  Sometimes you get lucky when you are drilling and it will loosen up and you can back them out with an E-Z out.  I only use the square E-Z outs any more.  I've not had any luck with the spiral and little luck with the square.  If you happen to have a mig welder and some stainless wire, you may have another option.  I've had the best success with welding up the end of the stud and then grabbing it with a pair of vise grips.  It's tricky but you just weld a little bit at a time, let it cool a little and add more material.  Once it's high enough to grab, quench it with cold water and let it cool completely.  The quenching breaks the corrosion loose and tends to make the stud easier to remove. This method is the least likely to damage the threads in the head. The stainless wire won't stick to the aluminum head which is the only reason this method works.

Regards,
Rich