Can a broken spark plug be removed with the head on?

[Sidecar Bob]

The 'Wing has been running a bit funny lately so I decided to check the plugs. 2 came out OK, one was a bit of a struggle and the 4th broke off. It is a clean break at the root of the threads.

I need to drive it to work on Monday so waiting for a head gasket is out of the question.

I do not have easy outs and can't get to a store to get them.

How can I remove it without taking the head off?

[Rat]

Cut a slot in it with a Dremel and use a big screwdriver

Gord

[BearWing]

What Rat said. I've done it several times. Take a needle-nose, and carefully break away all of the porcelain, and continue from there.

[Sidecar Bob]

I don't think that would work. The threaded part of the plug is all that's left (the ceramic part all came out) and even if I could get a Dremel into the plug well at the right angle to cut the slot it would be cutting into the head as well as the plug.

I am starting to think about drilling it out...

[roncar]

...The threaded part of the plug is all that's left (the ceramic part all came out) ...
I am starting to think about drilling it out...

BTDT! Even with the heads off, I still haven't got those bits out (of course I haven't tried in a while either.) Easy-out....no-go. Left hand drill bit....no-go. Drill....no-go. Copious amounts of penetrant was used in the attempts. The only thing I didn't try was heat. I replaced the heads so they're still sitting on a shelf in the shop waiting for me to get motivated again.

[Sidecar Bob]

I have been looking online. One guy got a broken plug out of his car by cutting the end in half with a "junior" hacksaw blade (I imagine this means a narrow one, and I think I have some of them). After he cut it he pushed the pieces inward by hammering on an old screwdriver and then was able to turn them out with the screwdriver.

I also found a couple of references to drilling it out, starting with a bit that's just bigger than the hole and working your way up to one size smaller than the inside of the threads, increasing the bit one size at a time so that the hole will keep the bit centred.

So it looks like its either sawing or drilling..... What do you think?

I should also mention that its on the side with the sidecar so even if I could wait for a gasket any attempt to remove the head would begin with:
1) re-install the centrestand.
2) remove the sidecar (involves removing the shelter & seat and unplugging all the wiring)

[robertoman69]

Got a pic of the broken plug?

[Sidecar Bob]

Not much to see. It broke off flush with the head. When you look into the plug well it looks like someone drilled a small hole instead of the normal one.

[vapor_trail]

I bet a high end air chisel could cut a decent slot into the thread and not mutilate the head. the hammering would upser the threads a bit also, might just spin loose with the air chisel.

[Sidecar Bob]

Well, I decided to drill. I figured I might not be able to keep the saw out of the threads and I liked the idea of the hole keeping the bit centred.

I took my time and made sure each bit was nice and sharp and picking up the swarf with a telescoping magnet between bits. As soon as the hole was big enough for the magnet to pass through I started fishing the swarf out of the cylinder too. Starting with 11/64 and working up to 19/32 (I measured the non-threaded part of a spare plug), it took about an hour and a half including sharpening most of the bits and spending most of the time fishing with the magnet. I am about to duct tape a piece of clear tubing to the Shop Vac and see if I can pull anything else out of the cylinder.

The good news: As I started to run the last bit in it jammed so I reversed the drill and the remains of the plug came out with it, including the side electrode.

The bad news: About 1/4 of it is missing and one side of the hole looks like it only has about half of the threads. My poor man's thread chaser (an old plug with 4 slots made with a cutoff disc in the angle grinder and the side electrode and gasket removed) went in easily so I think I'll put a plug in and see if it starts.

Will it be safe to drive it this way? I only need it for about 500-600 Km (about 300-375 miles) before the 650 will be ready and I can deal with it in the spring - maybe a Thread-Sert?

What do you think?

[scootsx2]

Man, talk about brute force.

[Greg]

I think it will start. But what will the escaping gasses do to the plug hole if there are any.

Greg.

[vapor_trail]

i thyink it'll be fine. put a big gobber of pipe tape on the plug. before starting, run it a bit with the plug rempoved, let it blow out what's stll lurking in there.

[Sidecar Bob]

Yeah. I did crank it over with the plug out for a few seconds after I vacuumed it (I had to use smaller tubing because the OD of 1/4" as too close to the hole size so it couldn't suck). You are kidding about the pipe tape, aren't you?

The face of the head that the plug seals against is OK and the missing threads are at the cylinder end of the hole. The drill was pretty well centred where it went in but somewhere along the line, in spite of using 16 bits so that the hole would pull the bit straight each time, it went off by about a degree.

It started OK but I wonder if the missing threads will either reduce the holding power or become a place for carbon to build up that will interfere with future plug removal.

BTW: I think I may have found the cause of the rough running. I had to un-bolt the intake manifold and rotate it out of the way (yes, I did stick a sock in the head's inlet. Literally) and when I went to put it back I noticed a crack between the rubber and the metal.

[KYpondman]

A case for using anti-seize compound!
Claude