Broken spark plug advice

[winchman]

Got a Honda C90 Type engine, the 10mm spark plug is sheared off and the ceramic is out leaving a steel threaded sleeve in the alloy head.
Any top tops for removal?
I have soaked in Plus gas, tried various easy out type things and heat, but how hot should I get it and how would I know?
Anything I am missing?

 

[GraemeVW]

Ally head?
If so, if heat it untill the easy out backs it out.
The ally will expand enough before it melts. I can't see a situation happen where it wouldn't let go before anything bad happens.

Try getting it as hot as you can with an air gun, or putting it in the oven.at 150°.

On my bike the oil pump is fitted like that, get the ally case to 159 degree and the oil pump slides in/out, but there is enough contraction that you have no chance of getting it out cold.

 

[winchman]

Thanks Don't really want to strip it as I am selling the bike, just more chance of a sale with the broken plug out, I do have a spare head to throw in the deal but it puts a few people off having to strip the head off to use it.
I have been using my Mapp gas torch but don't want to over heat it, its showing no sign of movement yet will try again tomorrow.

 

[GraemeVW]

Thanks Don't really want to strip it as I am selling the bike, just more chance of a sale with the broken plug out, I do have a spare head to throw in the deal but it puts a few people off having to strip the head off to use it.
I have been using my Mapp gas torch but don't want to over heat it, its showing no sign of movement yet will try again tomorrow.

Ah, I see.
Slightly different situation.
I can't see it taking much more than 200°, of its ally head.

Round headlight c90?

If so, ignore all I've said. Impossible to get it out. Bikes shagged. I'll give you £25 for it.

 

[winchman]

Ah, I see.
Slightly different situation.
I can't see it taking much more than 200°, of its ally head.

Round headlight?

If so, ignore all I've said. Impossible to get it out. Bikes shagged. I'll give you £25 for it.

Its a 78/79 C70, thanks for the offer is it just the head light you want???

 

[8ob]

Even if you got whats left of the plug out I reckon the thread will be following it.Just sometimes its better/quicker not to fanny about and just drill/helicoil.

Bob

 

[GraemeVW]

Its a 78/79 C70, thanks for the offer is it just the head light you want???

Cubs were £25 a piece when I was 12. I assume they are still the same price?

 

[GraemeVW]

Even if you got whats left of the plug out I reckon the thread will be following it.Just sometimes its better/quicker not to fanny about and just drill/helicoil.

Bob

I've never stripped a thread removing stuck stuff, only when torquing up things which weren't stuck when taken apart!

Get it hot enough to expand the head and I'd have thought it would be fine.
Force it put, and maybe not.

I imagine what kills the thread is if what's out the other end is rusty and damaged and that's what you wind back through once it starts to move?

Edit...
I've never had a stuck plug though, only bolts and studs, and plenty snapped flush.

 

[RichardM]

Snapped the nut off I assume. Can you weld a nut to the remainder of the plug?

 

[winchman]

Snapped the nut off I assume. Can you weld a nut to the remainder of the plug?

Yes Nut and ceramic came straight out left a threaded sleeve behind.
No welder where its stored and its not the best access
My straight east outs grip it but feels like I will snap them before it moves, left it soaking again over night

 

[winchman]

I've never stripped a thread removing stuck stuff, only when torquing up things which weren't stuck when taken apart!

Get it hot enough to expand the head and I'd have thought it would be fine.
Force it put, and maybe not.

I imagine what kills the thread is if what's out the other end is rusty and damaged and that's what you wind back through once it starts to move?

Edit...
I've never had a stuck plug though, only bolts and studs, and plenty snapped flush.

The end should be fine as it will or should be flush with the spark plug thread

 

[winchman]

Ah, I see.
Slightly different situation.
I can't see it taking much more than 200°, of its ally head.

Round headlight c90?

If so, ignore all I've said. Impossible to get it out. Bikes shagged. I'll give you £25 for it.

Even we where amazed when we saw one go at auction for almost 4K! Nothing special either.
A non runner restorable should fetch £250-£1000, especially off tax and MOT exempt
Jap Imports are very nice £1500-£2000 depending on condition.
Early pushrod stuff is sought after but I know nothing about them
I assume everyone is off to the shed now looking for the Cub they parked years ago????

 

[GraemeVW]

Even we where amazed when we saw one go at auction for almost 4K! Nothing special either.
A non runner restorable should fetch £250-£1000, especially off tax and MOT exempt
Jap Imports are very nice £1500-£2000 depending on condition.
Early pushrod stuff is sought after but I know nothing about them
I assume everyone is off to the shed now looking for the Cub they parked years ago????

They all got nicked in the late 80s, ridden to death by kids, then dumped in the canal/woods.

I looked at a blue one about 10 years ago, complete heap, he wanted £400, I couldn't believe it.
Shame

 

[GraemeVW]

The end should be fine as it will or should be flush with the spark plug thread

Yes, exactly. So get the head hot and it should wind out.

Never got to the bottom of the head material situ. Alloy or iron?

 

[winchman]

Alloy

 

[GraemeVW]

Alloy

Ok, good.
I just can't see damage from heat occurring before it's expanded enough to free what's left of the plug. I'd just heat, try, heat, try till it goes.

 

[Pete.]

Grind the back off a 32tpi hacksaw blade and put it in a pad saw handle. Use it to cut the thread ring then tap it loose.

 

[Gareth J]

You could try a very gentle impact wrench on whatever you're grabbing onto. Lots of small impacts might loosen more effectively than more torque.

 

[8ob]

Get a lot of this on saws and stationary engines, its normally corrosion between the plug and head, other times its carbon buildup on the exposed thread inside the cylinder head. Either way you tend lose the thread when undoing the spark plug, op`s head has the plug seized to the point the thing has sheared off completely, I wouldn't be holding out much hope on that one. As with all this stuff the remedy is quicker than beating the ideas about.

Bob

Installing inserts is as easy as this

 

[Brad93]

Weld a nut to it if you can