I have a taotao atv, 125 cc, with a broken exhaust stud, of course slightly recessed in the engine block.

Here is what I did to fix it:

Well, it's never pretty !

The exhaust stud is a nightmare.  The angle of it, combined with where it's mounted (the engine) means you can barely get in there.

Go to FLAPS (Friendly Local Auto Parts Store), and buy an extractor for broken bolts.

Oh well, i tried anyway, because I'm an idiot and don't know when to quit.

Drill bit, snapped off.

Remember, I'm an idiot and don't know when to quit.

Drill again, break another bit.

Go to O'reilly's pay 10 bucks for a "titanium" drill bit.

Drill again, gets a bit further, maybe a little bit further than 1/4", breaks again.

Remember I'm an idiot and don't know when to quit.

Pound extractor into drilled hole, it bites into it, i'm thinking, shit, this might work even though I'm an idiot.

Try and turn extractor, 3/8" to 1/4" socket adapter snaps off in socket wrench, when did metal get so weak as I know I ain't that strong ?

Remember I'm an idiot and don't know when to quit.

Back to O'reilly's pay 10 bucks for 3/8" to 1/4" socket adapter with lifetime warranty, thinking I should start buying O'reilly's stock.

Try and turn extractor, extractor breaks off.

Remember it's 100+ degrees, so I'm in a rosy mood, F***!

I finally know when to quit, bolt exhaust / muffler back together with one bolt and declare that it will just have to do.

Order new engine with starter and transmission, 249.00, bolt in replacement!

Then I head out with Grandpa for a beer, only smart thing I did all day.