Welcome to the (unwelcome !) club. I to broke not 1 but 2 exhaust studs off on my 1981 XJ650.
I also tried stud extractors but unless you can drill the hole exactly in the centre then the extractor does not appear to work ( well it didn't for me).
I also used gentle heat and soaked the stud with lots of WD40. In the end (because the down tube was in the way) I droppped the engine out , not easy as its a 4 cylinder engine. Once on the bench I was able to get a small punch onto the edge of the broken stud and lightly tapping it slowly removed the stud in 10 mins - the lead up to getting the engine onto the bench took weeks as I lost interest and motivation.
Once the stud was out I undertook a rebuild of the frame ( a split was found when removing the engine !) the frame welded up then shot blasted and power coated. The top half of the engine was soda blasted and repainted by hand and then the engine re-installed. But as I installed the exhaust I broke a second stud I nearly cried ! Well the engine was out in one and a half hours and the broken stud drilled out and a new thread cut in the same morning.
Today I collected the tank, side panels, front mudguard and seat cowl from an application of new decals and a re-spray ready for fitting
Only major job left is carb overhaul and a new MOT
So two different solutions - hope they help , as it is possible to remove broken studs - Good Luck [smiley=thumbsup.gif]
