Author Topic: Spark plug disaster  (Read 3784 times)

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Offline gregwaits

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Spark plug disaster
« on: May 28, 2008, 12:17:07 PM »
This is pretty messed up. I was in the process of changing the plugs on my CB750 and the plug for cylinder one broke off at the bottom. (see pics)

Will I be able to somehow tap into what is left in the head, or do I have to remove the cylinder head.

I wish the that these issues would quit popping up so I could begin to enjoy riding the bike!

Grrr
1978 CB750K8; 1970 CB450

Offline ger87410

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Re: Spark plug disaster
« Reply #1 on: May 28, 2008, 12:25:11 PM »
Looks like the threads broke in half.  :o

My money is on a head removal.  Especially since it's the #2.  There's no way you could cut a slot in that and then turn it.

Maybe CB-welding something to it and turning it that way?  :-\

Offline tsflstb

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Re: Spark plug disaster
« Reply #2 on: May 28, 2008, 12:25:29 PM »
I feel ya.



This is on my BMW so access is a lot easier.  I'm soaking it in penetrant and using the heat gun on it.  A few more days and I'll try the square EZ out.  I figure worst case it will break off to and I'll have to pull the head.

You can try a drill bit and tap with lots of grease to catch the shavings, I'd be worried that something would fall in there.

Offline gregwaits

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Re: Spark plug disaster
« Reply #3 on: May 28, 2008, 12:28:58 PM »
Actually the problem is in cyl # 1. I can look down in there  easily enough.

My mechanic just told me to spray blaster down in there and let it sit for a day or three. Then use one of those reverse thread "easy out" devices (which of course I will have to go buy now lol).

He said it should work. Since more than half of the threads are still in the cylinder head, maybe it will.

We'll see.
1978 CB750K8; 1970 CB450

bhorocks

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Re: Spark plug disaster
« Reply #4 on: May 28, 2008, 12:29:29 PM »
all i can say is that sucks...

Offline Steve F

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Re: Spark plug disaster
« Reply #5 on: May 28, 2008, 12:58:28 PM »
The problem with trying one of those "easy-outs" is you have to have a through hole for it to go into.  With a through hole, that means you have to knock out the ceramic in the middle first, which is likely going to end up in the cylinder.  Not good (unless you can figure a way of vacuuming all the little bits out of the cylinder.... :-\
If it were mine, the head would need to come off, or you take a risk of all those ceramic pieces destroying the cylinder.

Offline ger87410

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Re: Spark plug disaster
« Reply #6 on: May 28, 2008, 01:08:15 PM »
The problem with trying one of those "easy-outs" is you have to have a through hole for it to go into.  With a through hole, that means you have to knock out the ceramic in the middle first, which is likely going to end up in the cylinder.  Not good (unless you can figure a way of vacuuming all the little bits out of the cylinder.... :-\
If it were mine, the head would need to come off, or you take a risk of all those ceramic pieces destroying the cylinder.
Personally, I'd remove the head rather then risking a rebuild of the cylinders...

Your comment on vacuuming gave me an idea.  U could hook up a small hose/tube to your vacuum hose using duct tape and vacuum the cylinder out after removing the broken plug.  It'd still be risky since you're not guaranteed to get all ceramic pieces.

Offline tsflstb

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Re: Spark plug disaster
« Reply #7 on: May 28, 2008, 01:31:49 PM »
Actually the ceramic (at least on my bike) came out in one piece with some needle nose pliers.  The pic was before I even tried that.  I thought it would be stuck in there, but it came out easy.  I can only hope the rest of it will follow.

There is still the electrode on the bottom of the plug threads, so you don't have unlimited space.  Plus the piston is down there somewhere too.  Might have to check with a flashlight and bump the engine over to get it as far away as possible.

Offline andy750

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Re: Spark plug disaster
« Reply #8 on: May 28, 2008, 01:37:22 PM »
I had a spark plug hole on #2 helicoiled with engine in the bike and vacum used to suck up all the waste....it can be done!

good luck
Andy
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Offline chrislib

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Re: Spark plug disaster
« Reply #9 on: May 28, 2008, 03:24:54 PM »
Be very carefull NOT to break the easy out, I don`t think there is a drill bit made that`ll cut into one of those (don`t ask,lol). Also try to get the area heated up good before laying into it, one of those square halogen work lamps works well (don`t want to get it TOO hot). Good luck.
Chris...closet Idlefiddler
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Offline nilsey

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Re: Spark plug disaster
« Reply #10 on: May 28, 2008, 03:30:26 PM »
Actually the problem is in cyl # 1. I can look down in there  easily enough.

My mechanic just told me to spray blaster down in there and let it sit for a day or three. Then use one of those reverse thread "easy out" devices (which of course I will have to go buy now lol).

He said it should work. Since more than half of the threads are still in the cylinder head, maybe it will.

We'll see.

this same thing happened to me.

do what your mechanic says -- it will work. be patient and spray the stuff in there and wait and slowly ease it out.

this is what taught me never to overtighten spark plugs.....
1976 CB550K: stock airbox, cb650 cam swap, 4x2 exhaust, dual disc brake conversion.
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Offline TwoTired

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Re: Spark plug disaster
« Reply #11 on: May 28, 2008, 03:36:44 PM »
Doesn't aluminum expand with heat? Won't that make the thread hole tighter?  Now, making the spark plug thread metal colder, ought to shrink that away from the thread groves.  Dry ice? Cold spray?

As a penetrant use auto trans fluid and acetone 50/50 mix.
Lloyd... (SOHC4 #11 Original Mail List)
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GraveRobber

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Re: Spark plug disaster
« Reply #12 on: May 28, 2008, 03:37:17 PM »
I did the same thing one time on a chevy 350. Threads snapped off the plug but everything else came out. Try it, It worked for me. You might have to put a socket on the ez-out to get the reach. Just take it slow.

Offline kghost

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Re: Spark plug disaster
« Reply #13 on: May 28, 2008, 04:12:02 PM »
Man that sucks....

And the easy out will just deform whats left of the plug as you try and get it out.

Camming on the inside of the circle and what not.

It can be done but it takes finess.

I always us anti-seize on the plug threads for that reason...betting the PO didn't.
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Offline Johnie

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Re: Spark plug disaster
« Reply #14 on: May 28, 2008, 05:16:46 PM »
Man, that can turn a nice day into crap.  The pics make me sick.  I agree, I have been using anti-seeze since I got the KO running.  Sorry that is too late for you but I wish you the best in getting that sucker out...
1970 CB750K0 - Candy Ruby Red
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1976 GL1000 Sulphur Yellow

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Offline Steve F

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Re: Spark plug disaster
« Reply #15 on: May 28, 2008, 07:07:55 PM »
Be very carefull NOT to break the easy out, I don`t think there is a drill bit made that`ll cut into one of those (don`t ask,lol).
Hence the old phrase "........more f*[k3d up than a busted easy-out"   :D

Offline Raul CB750K1

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Re: Spark plug disaster
« Reply #16 on: May 29, 2008, 01:55:35 AM »
That broken plug sucks, but it is indeed a great mechanical challenge. You will end wiser and more expert when you have it out.

I had an easy out broken in a stud, and I don't plan to use them anymore. I now drill the broken stud as if I'm going to insert the easy out, but gradually increase the drill diameter to eat the whole stud remains. I then tap new threads when I'm done, and if I can't, use a helicoil. It takes less time and the result is better.

Offline 750K2

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Re: Spark plug disaster
« Reply #17 on: May 29, 2008, 06:00:28 AM »
Doesn't aluminum expand with heat? Won't that make the thread hole tighter?  Now, making the spark plug thread metal colder, ought to shrink that away from the thread groves.  Dry ice? Cold spray?

As a penetrant use auto trans fluid and acetone 50/50 mix.

two tired - i was a thermodynamics major in college and we did a calculation that shows that adding heat to a hole, in metal materials causes expansion, not contraction.  i'd use heat - and no anti-seize as the plug is supposed to be grounded to the metal casing.
frank

Offline Bob Wessner

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Re: Spark plug disaster
« Reply #18 on: May 29, 2008, 06:20:55 AM »
Doesn't aluminum expand with heat? Won't that make the thread hole tighter?  Now, making the spark plug thread metal colder, ought to shrink that away from the thread groves.  Dry ice? Cold spray?

As a penetrant use auto trans fluid and acetone 50/50 mix.
adding heat to a hole, in metal materials causes expansion, not contraction.frank

Same technique is used to insert wheel bearings. Granted, in that case the hole is empty, but in the case of the plug, the alum. will expand faster than the steel.
We'll all be someone else's PO some day.

Offline kghost

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Re: Spark plug disaster
« Reply #19 on: May 29, 2008, 06:29:03 AM »
Doesn't aluminum expand with heat? Won't that make the thread hole tighter?  Now, making the spark plug thread metal colder, ought to shrink that away from the thread groves.  Dry ice? Cold spray?

As a penetrant use auto trans fluid and acetone 50/50 mix.

two tired - i was a thermodynamics major in college and we did a calculation that shows that adding heat to a hole, in metal materials causes expansion, not contraction.  i'd use heat - and no anti-seize as the plug is supposed to be grounded to the metal casing.
frank

If you don't use anti sieze when you reinstall a plug stick to thermodynamics.

There will be less busted plugs for the rest of us.
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Offline Steve F

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Re: Spark plug disaster
« Reply #20 on: May 29, 2008, 06:33:40 AM »
I use anti-seize on plugs too.  Better safe than sorry, and no problem with plug grounding.

Offline 750K2

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Re: Spark plug disaster
« Reply #21 on: May 29, 2008, 06:42:31 AM »
i stand corrected on the anti-seize.  looked it up in a haynes manual.  thanks!

Chad

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Re: Spark plug disaster
« Reply #22 on: May 29, 2008, 07:25:47 AM »
I gotta get me a bucket of antiseize. I've  been using antifreeze.  I guess I misheard what that guy told me.   ;D

Offline kghost

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Re: Spark plug disaster
« Reply #23 on: May 29, 2008, 07:49:17 AM »
Antiseize doesn't inhibit conduction.

Plus its on the threads and the plug bottoms out on its sealing washer and the head.

Ground isn't a problem.

Mainly what it does is keep the exposed tip of the plug that protrudes into the combustion chamber from deteriorating....

Keeps the dissimilar metal galling/sticking to a minimum....

Lets you get the plug back out without snapping one off.
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Offline TwoTired

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Re: Spark plug disaster
« Reply #24 on: May 29, 2008, 10:39:26 AM »
Doesn't aluminum expand with heat? Won't that make the thread hole tighter?  Now, making the spark plug thread metal colder, ought to shrink that away from the thread groves.  Dry ice? Cold spray?

two tired - i was a thermodynamics major in college and we did a calculation that shows that adding heat to a hole, in metal materials causes expansion, not contraction.  i'd use heat - and no anti-seize as the plug is supposed to be grounded to the metal casing.
frank
Frank,
No sir.  You would have to heat the entire head to get that hole to expand and those temps would likely char any oil inside.  The threaded hole is constrained by the surrounding mass of the head casting.  If you heat just the thread hole, the aluminum expands in that area but the only place it has to expand into the where the steel spark plug remains are, making it grip even tighter.   Aluminum expands faster and at greater volume than steel which would make the interface between them even tighter.  Further, the head is designed to move heat from the hole to the cooling fins.  Thereby, the entire mass of aluminum of the head will try to expand in all directions.  Such expansion forces will tend to make the hole diameter smaller, as that hole is a stress reliever for the surrounding mass of metal (barring the steel now embedded there).  I simply don't believe your calculations ever addressed a metal mass as complex as a cylinder head.  If the metal being heated was a simple unconstrained ring, then yes, the hole and the outer diameter would expand.  But, if you hold the outer diameter in place physically, the inner diameter, being the only area to expand into, will diminish.  A metallurgist and some welders know these things, if not by training, then by experience, which is where the college boys find their calculations have missed several variables that should have been included in the equations.  Materials science and thermodynamics are related, but NOT the same thing.

Anyway, it's the relative temperature between the steel (now stuck in the aluminum head), and the head itself that is the goal.  Dry ice/cold spray, if applied quickly enough to the inner steel, WILL contract/shrink the steel.  Then it is a matter of the conduction rate between steel and aluminum as to which one contracts faster.  It's a pity that an easy-out will exert outward pressure on the steel, increasing the friction between steel and aluminum.

Heat on the other hand, may just change any glue properties bonding the steel to the aluminum threads (like burnt oil).  Turning that glue to ash may well make extraction easier.  But, I'd let it cool before the extraction attempt.

I agree wholeheartedly about the anti-seize, btw.  But, that's a preventive, not a cure at this point.

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
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