Before you guys blast me, I know I screwed up. Don't know why I was successful on three carbs and I failed on one.
What did I do?
Several years ago, I removed (3 of the 4) mixture screw plugs in my '94. I was only partially successful on the 4th. Yeah, I now know the proper technique, but unfortunately I didn't go that route.
So, any ideas on getting out what's remaining of the 4th plug? There's about 1/4" of material left with about a half a millimeter less diameter than the bore of the screw gallery. Basically it's a 1/4" cylinder with an off-center bore in the bottom of the hole.
I've tried grabbing it with a coarse thread machine screw. I've half-heartedly attempted to "fold" the cylinder inward so I can grab it with a probe.
Neither worked, but I'm leary of putting too much pressure on it for fear of driving the screw into the seat.
I just recently fixed a lathe that one of my wonderful students broke. I used a left hand twist drill. Turn it counter clockwise in your cordless drill. Worked perfect.
Be sure to use penetrating oil first and center punch what is left of the screw.
Good luck and don't go too deep.
" Faster Horses, Younger Women, Older Wiskey, More Money."
I successfully drilled a couple of mine out before using a bit about half the size of a mix screw. Just need to be very careful and do not too deep. once you get through the main body, pick the parts out with a "pick" carefully and the threads shouldn't get damaged. Worked well for me.
Tip: Find something to go over the drill bit to keep it exactly centered in the bore. I found this vacuum line fitting in my toolbox that worked perfectly.
Once you've drilled into the screw a little ways, you may have some luck with a screw extractor tool. I chose this one as I didn't want the left-handed screw in type - I was afraid it would put too much expansion pressure on the soft metals.
The left hand wound drill worked for me. first I drilled a center with a 1/4" left hand drill. with this accurate center I used a smaller left wound drill and the threaded porthion came right out. Then I fished out the needle and washer, spring and o ring. which were dissconnected with the first small drilling.