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Broken Spark Plug in Threads - not a GS

tas850g

tas850g

Forum Mentor
Sorry for posting this in this forum but i need help.

I was removing my spark plugs today and either I or the PO broken the badly corroded plug off in the cylinder. The porcelain is out but the bottom half is still in the threads. All there is left in the cylinder threads is the old plug thread "ring". Not sure what you would call it. THe electrode is still in there too.

This is on the 1985 Ninja 600zx.

How the heck am i going to remove this? The plug is a 10mm I think, NGK D9EA.

I sprayed some PB blaster into the plug hole a few time to anticipate some type of removal. I just need to know what is the best first time removal method would be.

I would be willing to taking the entire bike to a machine shop.

Plugs #1 & #2 are out but #3 is not budging yet but I'm trying to be patient and let it set a few days in the PB Blaster to see if that will help with the removal.

Any and all advice will be helpful.
 
yes let it soak a few days and reapply the pb a few times as well.. in the meantime post few pics to get a better view of whats left in there. Some possablities that may work is to weld a big bolt to the remaining bottom part if you can get to it and gently try to get it to wiggle both in and out a bit. Working it both ways does two things. First it will sort of grind up the crud in the thread and loosen that and it will create gaps for more PB to work its way in deeper
Second possibility is to buy a big left handed thread tap and start it down the center. the left turning cutting action should grip the threads and help back it out that way. just be sure to get a tap that will grip the ID and not big enough to hurt the original threads in the head.
If the square part that the socket grip on is still there you wont need to weld on a bolt though.. just lots of heat from your propane torch and more PB will probably loosen it up . Again the wiggle back and forth theory applies to try and breakm up the oxidation and allow the PB to get in deeper.. but first lets see pics to get a clear analasis of what left to work with... and when you get it all out safely be sure to blow the crap out of that cylinder with lots of compressed air, or use a pencil magnet to be as sure as you can absolutely be that there isnt one sliver of metal in that cylinder before it is turned over!!!! Do both to be safe.
 
Last edited:
the porcelain and the metal hex of the plug is out but the threads is still in there. I don't have a digital camera at home to take a picture of the removed plug. I'll take a pic tomorrow and post it after work.
 
IMO to get out what you describe the cylinder head should come off.

NGK D series plugs are 12mm thread - with the porcelain gone and the side electrode clipped off you should be able to use an 8mm or 5/16in tap from the combustion chamber side - a normal R/H tap will push the remains out the top of the plug hole.

It's an ugly problem with no easy fix.

Greg T
 
i would hate to take the head off but i think that would be the best way. Trying to figure out if there might be something else to try first.

I'm afraid of the whole timing chain/tooth jumping and throwing off the timing among other things.

This is a project bike so there is no rush to get this done.
 
well now that i understand whats left in there i would tend to lean with taking the head off as well. may have to bite the huge got you by the nads bullet and take it into a repair shop if your not confident in messing up the timing or cams or whatever.. then again see what members are in the general area you are in and whisper sweet nothings in an ear or two and see what you guys can work out.. Even a few hundred and a day spent learning and making a new buddy is way cheaper than the dealership option... oh and be sure to find out what the guys favorite beer is. have some good and cold and send a case home with him as well...
 
Can you take a bolt of the appropriate size, grind it down to fit, and weld it to what's left of the spark plug? Should let you twist it out?
It always better not to remove a head if it's not absolutely required.
 
never had this happen with a spark plug, but with bolts that were broken off flush with the head surface. if you or someone you know is good with a welder, I'd try welding a bolt to it and working it in and out a few times before going right to taking the head.... a couple of weeks ago it took me 8 welds, but I finally got the snapped bolt out without having to remove the head....
 
Carefully drill and tap with the head on if accessible. make sure the intake valve is closed. Grease the drill, grease the tap. Wash the cylinder out well through the spark plug hole with brake cleens and compressed air. Oil the cylinder, screw in the new plug, cross your fingers and pull the rope.
I have done this on a about 8 or 10 neglected car spark plugs. I ended up pulling the head only once. (to retrieve the pesky side electrode)
 
the plug broke below the porcelain so i can see the electrode.

I think it broke for a few reasons, one being it is corroded.

I did take out #1 and #2 but #3 is not moving after applying a descent amount of force compared to the other 2 plugs that i removed.

According to the manual i don't have to take the engine out to get the head off.

So over the next days/weeks i'll start tearing it down. There is very little room to work with in the plug hole plus the hole is pretty deep.

Thanks for the advice everyone. I'll try to take pictures.
 
pics would def help, so we can see what you're dealing with....
 
Ughhhhh!

Ughhhhh!

One thing you may have going for you......it's probably not in there extremely tight so if you could just figure out a way to get a little universal, counter clockwise pressure on it, it might come out fairly easily. Good luck!:)
 
Have you tried some sort of penetrating oil like wd-40, pb blaster, or kroil to loosen it up some?
 
i've been soaking in with PB blaster since sunday. I know most of it goes down into the cylinder but i keep soaking it anyway. I think i'm going to try the easy out just for kicks, going nice and easy. If i see anything bad then i'm stopping. Going to put the piston TDC as much as i can, vacuum out pre, during, and post.

I've got the valve cover manifold off so it gives me a little more room to work with.

I currently don't have a camera to take pics.
 
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