Removing broken bolts?

[Futuramic]

I have an issue with a petrol generator I have owned for a while. It is as old as the Ark and worth little; but is a powerful beast producing 2Kv single phase. It would be worth fixing. The alternator is fine, but the engine has issues. It is a Briggs and Stratton I/C series sidevalve (I said it was old!) probably the 8 HP model with a downdraft carb. It runs like a watch, or at least it did. When I got the thing the exhaust silencer box was full of holes so the engine produced more noise than an Iron Maiden concert. I decided to replace the silencer but the bolts have broken.

The bolts were extremely long, which is part of the issue, and both sheared neatly off level with the exhaust port. I have stripped the engine and found that the exhaust port is cast into the block itself. It is a true flathead type engine, which makes things trickier. I can't just go and get a new head from somewhere.

The bolts were of very small diameter. Does anyone have any ideas?

[M4cruiser]

Although I'm not familiar with the engine you describe, here are some general ideas for this kind of situation:-

You can buy a bolt remover which is basically a screw with an anticlockwise thread.

You may need to heat up the surrounding metal near the remains of the bolt (which makes it expand and therefore helps to ease the clearances, the bolt expanding less than the surround).

Can you get any "dismantling oil" into the threads? I have found the 3-in-1 brand to be ok - better than WD40 for this specific use.

Good luck,

[HustleRussell]

^ EZ-outs are seldom effective in my experience. I'd be drilling and tapping new threads if possible. I find this kind of job soul destroying so if I was having a weak moment I'd entrust this to my local engineering shop who would probably extract the bolts and repair the threads for about £30, which is cheaper than hours of work, several drill bits and an EZ-out.

[GraemeP]

Nowhere near as challenging, but we had some counter sunk bolts in a steering wheel / boss that had rounded off heads. We drilled out (use a Henry to suck the bits away whilst drilling), then tapped.

[mgtony]

Don't bother buying the cheap thread extrator kits, they're useless. These aren't bad quality available from Cromwell Tool branches. All depends on how tight or rusted in the bolts are.

http://www.cromwell.co.uk/KEN0751160K