Cross Threaded Spark Plug

yozalo · 05-07-2011, 09:06 PM

Was removing the spark plug, and during installation of new one, the threads got cross threaded. The spark plug is no longer tight, and when tightening, it keeps on turning without wanting to stop even though threads are all the way in. I have two options I can think of on top of my head right now:

a) I can either purchase a heli coil kit. I've never done it before but looks like a simple process according to youtube videos. Will cost around $30 - $40...

b) I can purchase a new cylinder head. Will cost $30 - $40....

Purchasing a new cylinder head looks like the best decision, unless there are cheaper options out there.

FLASHLIGHTBOY · 05-08-2011, 12:12 AM

the helicoil is easier.. the head you have to replace which is more work... you can always do the repair of the sparkplug hole after to have a spare head.. I would think if your skills ( and luck ) are limited.. then change the head.. I guess it is a lesson learned about spark plugs.

Weldangrind · 05-08-2011, 12:08 PM

The trick with a thread insert is to get all of the schrapnel out, and it's tough to do. If there are any shavings left over from drilling and tapping, it could score the cylinder (less likely) or damage the piston (more likely). The only way I'd do a thread repair is to remove the head, in which case you might as well replace it. Is there a big bore kit that you can install while you're at it?

On the plus side of thread repair, a thread insert is a permanent fix that isn't likely to ever strip again. Also, look for Perma-coil, which is a little cheaper.

In the future, use a little anti-seize on the threads to help prevent cross threading, and always thread the plug in by hand until you're sure it's started.

yozalo · 05-08-2011, 01:26 PM

Thanks for the help.......Either way I will have to remove the head. I could either heli coil it...or perhaps get a new cylinder head. A big bore kit will cost a leg and an arm, I checked the price and it's coming to $150 to convert a 110cc to 114cc...not worth it at all...

Why...oh Why did I not use anti seize from the beginning, had some laying around. But anyhow....how hard is it to heli coil the head, only reason I'm sticking towards heli coil is the fact that the problem won't probably occur again with it....

Weldangrind · 05-08-2011, 03:40 PM

It's not hard at all. The kit will probably come with the proper tap and the installation tool. Once you drill out the hole (to the size recommended on the package), you tap out the hole and then thread in the insert. Once it's in, you hit the installation tang with a punch and break it off. Done.

yozalo · 06-28-2011, 09:21 PM

I bought a new cylinder head, and finally received it after the canadapost strike.

Anyways, the cylinder head has some scratches on the ports. Is this something I should be concerned about? The scratches can be felt with your fingers:

Weldangrind · 06-29-2011, 12:05 AM

Typical China quality control. If it bugs you, you can sand out the scratches with some fine sandpaper. Don't do that on a gasket surface unless you're using a sanding block, and be sure to sand in an X pattern. Be gentle.

05-07-2011, 09:06 PM	#1
yozalo Join Date: Apr 2009 Posts: 330	Cross Threaded Spark Plug Was removing the spark plug, and during installation of new one, the threads got cross threaded. The spark plug is no longer tight, and when tightening, it keeps on turning without wanting to stop even though threads are all the way in. I have two options I can think of on top of my head right now: a) I can either purchase a heli coil kit. I've never done it before but looks like a simple process according to youtube videos. Will cost around $30 - $40... b) I can purchase a new cylinder head. Will cost $30 - $40.... Purchasing a new cylinder head looks like the best decision, unless there are cheaper options out there.
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05-08-2011, 12:12 AM	#2
FLASHLIGHTBOY Join Date: May 2009 Location: SASKATOON Posts: 1,161	repair the helicoil is easier.. the head you have to replace which is more work... you can always do the repair of the sparkplug hole after to have a spare head.. I would think if your skills ( and luck ) are limited.. then change the head.. I guess it is a lesson learned about spark plugs. __________________ DEALER FOR ZSTAR & GIO PRODUCTS, TAOTAO ABIBABA ATV ETC
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05-08-2011, 12:08 PM	#3
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	The trick with a thread insert is to get all of the schrapnel out, and it's tough to do. If there are any shavings left over from drilling and tapping, it could score the cylinder (less likely) or damage the piston (more likely). The only way I'd do a thread repair is to remove the head, in which case you might as well replace it. Is there a big bore kit that you can install while you're at it? On the plus side of thread repair, a thread insert is a permanent fix that isn't likely to ever strip again. Also, look for Perma-coil, which is a little cheaper. In the future, use a little anti-seize on the threads to help prevent cross threading, and always thread the plug in by hand until you're sure it's started. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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05-08-2011, 03:40 PM	#5
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	It's not hard at all. The kit will probably come with the proper tap and the installation tool. Once you drill out the hole (to the size recommended on the package), you tap out the hole and then thread in the insert. Once it's in, you hit the installation tang with a punch and break it off. Done. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

06-29-2011, 12:05 AM	#7
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Typical China quality control. If it bugs you, you can sand out the scratches with some fine sandpaper. Don't do that on a gasket surface unless you're using a sanding block, and be sure to sand in an X pattern. Be gentle. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

05-08-2011, 01:26 PM	#4
yozalo Join Date: Apr 2009 Posts: 330	Thanks for the help.......Either way I will have to remove the head. I could either heli coil it...or perhaps get a new cylinder head. A big bore kit will cost a leg and an arm, I checked the price and it's coming to $150 to convert a 110cc to 114cc...not worth it at all... Why...oh Why did I not use anti seize from the beginning, had some laying around. But anyhow....how hard is it to heli coil the head, only reason I'm sticking towards heli coil is the fact that the problem won't probably occur again with it....
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06-28-2011, 09:21 PM	#6
yozalo Join Date: Apr 2009 Posts: 330	I bought a new cylinder head, and finally received it after the canadapost strike. Anyways, the cylinder head has some scratches on the ports. Is this something I should be concerned about? The scratches can be felt with your fingers:
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