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Never seen this before, Sheared sparkplug.!!!

 
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megawatt
Speedway Rider
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Joined: 03 Apr 2009
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Location: Northiam, near Rye

PostPosted: Fri Oct 19, 2012 7:53 pm    Post subject: Never seen this before, Sheared sparkplug.!!! Reply with quote

Did a service on a mates 2002 ZX636 today. Everything went well until we put the last plug in , NGK CR9E. My mate is new to this, so he was screwing em in until the washer touched the head, tightening until the washer was crushed and then a slight nip up. He did not overtighten the previous 3 plugs. As he nipped it up, the spanner hit the frame??? He gently undid it and I retightened it. It went tighter and then went slack. I undid it all the way and then , oh my god!!
Old plug that came out

New plug.Came out eventually without removing cylinder head.



Neither of us is cack handed and at no time was the plug overtightened. I read somewhere that this has happened to a few people recently. Either NGK have made a bad batch or they are crappy copies, bought frrom a reputable motor factors. BEWARE!!!
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Simon Smith
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PostPosted: Fri Oct 19, 2012 10:13 pm    Post subject: Reply with quote

Not had that particular fault, but we've had several NGKs and Champions at work where the porcelain section has come loose and floats up and down. It seems that there are quality problems whatever the make.
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Carnage
British Superbike Racer
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PostPosted: Fri Oct 19, 2012 11:47 pm    Post subject: Reply with quote

not been unknown to have a duff new plug from NGK ....i.e new plugs fitted and the bike ran like a pig ......eliminated to 1 plug being duff
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Loco
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PostPosted: Wed Oct 24, 2012 11:26 am    Post subject: Reply with quote

Agreed, bad idle problems on the GSXR since I bought it were tracked down to a bad plug having only done 1700 miles !
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biggus
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PostPosted: Wed Oct 24, 2012 12:06 pm    Post subject: Reply with quote

Loco wrote:
Agreed, bad idle problems on the GSXR since I bought it were tracked down to a bad plug having only done 1700 miles !


Mental.

You do get premature failures, but it always suprises me when it's something simple like a spark plug... That said, the construction of a spark plug varies from manufacturer to manufacturer.

You'd think that it's one piece of material from the contact at the top to the electrode at the bottom... Wrong... there are different materials stacked to make the contact from that top part to the electrode, now, given that these are stacked, not welded, or bonded (although sometimes they use springs to maintain contact), it's no wonder that given the different expansion properties of each part could cause internal gaps to appear and cause internal arcing meaning that the resulting spark at the business end is less strong than it could be.
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