broken EZ-out

Hey everyone! Have a few questions about a broken EZ-out and the ensuing repair.

'81 KZ 750 LTD

Used a carbide drill to try and remove EZ-out/broken bolt and the carbide bit broke. Just my luck! Took the head to work because every other thing tried wasn't working. Use the "arc" machine to electrically bore the broken pieces out, now comes the problem.(will try and post picture later today)

Original hole is banged up a bit from trying other solutions, understand that I will probably have to Heli-coil for new threads. Still some..not much of the shoulder left for the guide sleeve, but chamfer is non-existent and just below at top of where the threads used to start looks ugly!!!! Actually can't see any at all!

1) Would it be easier to drill out remainder of other metals left over from extraction attempt and plug hole with aluminum and just re-tap? Hole is just a bit (.001, maybe .002) undersize from ID thread. Will double-check again tomorrow with gauge pins.

2) Have a machine shop do it? I would be doing it with a hand drill unless take back to work and use milling machine. Time constraints also.

3) If no drill, go machine shop...should I consider other things to be done to top-end and/or bottom end and at what cost. A few months left riding season here in the North East so $ not issue or time off bike, was my daily ride though.

I was thinking maybe polishing up the underside of head (a bit of carbon), maybe valves and one of those piston kits I've read about others putting in. Only just scratin' my head abit because of time and money (gasket kit) already spent and then the broken bolt. Unless someone tells me I can re-use the new gasket I'll need to purchase another and as you no not cheap, so was looking $ wise at using up the rest of the kit instead of it just tacked to the wall in the garage and possibly avoiding pulling anything off below valve cover for some time.

Bike was running great!!! New rear sprocket last year, 27K, everytihing stock except 4-1 and sprocket. Just got tired of seeing the oil/? dripping from the sides of the head (upon further inspection may have been the O-rings gone bad!)

Anyway, was hoping someone here may have some suggestions. If I get brave later this morning I may try another EZ-out in the now vacant cavity and see if I can break anything else loose or possibly use a bigger carbide drill and bore the hole a bit.

Thanks for any and all input!!!
Brad

I have pretty good luck with carbide bits but I use a SLOOOOOOW feed rate. Maybe .0001 - .0005 per revolution. You might try another bit but at a slower feed rate. Good luck.

Where is the location of the broken EZ-out? In all that write up, I don't think I saw anything about which bolt was trying to be extracted? Is the EZ-out still in the hole? If so, I am not sure a carbide drill bit will drill through it. A carbide cutter will cut it but that will really make a mess. Perhaps taking it to a machine shop would be prudent since you have few tools to remove the mess that has been made.

If coaxing and teasing doesn't work...
If you still have tool steel in the hole, find the machinist with the best 'touch' and use a carbide end mill. If you have carbide in the hole, use an EDM. If you still have part of the fastener in the hole, mill or drill on the mill. You can drill but only if you can get a flat and a good center to start.

If there is enough metal left, go with an insert for the guide hole and helicoil for the threads.

-Duck