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Discussion Starter #1
Any one ever heard of spark plugs coming loose? I was returning from a ride this afternoon when the bike sounded as if it broke a header pipe or blew an exhaust gasket. I thought that was possible as I only recently had the exhaust off, but on inspection, #2 plug lead was off and I could feel the plug loose in the head. No damage, it appears to have simply unscrewed itself and on checking the other 2 they were a bit loose too.
I fitted the plugs myself not 7 months ago so I know they were tight. Anyone ever seen this before?
 

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Never seen that happen! Maybe you didn't nip them down enough?
I always give that extra "nip" if you know what I mean, without going silly on it of course.

Strange...

Roden
 

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Discussion Starter #3
I'm always real careful not to overtighten then. Hate to strip one! It had to be #2 that came out and couldn't be refitted without taking the tank off.
Could be gremlins in my garage.
 

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It's been mentioned before. IIRC, at least 2 people on this forum have had their motors fragged this way.

Personally, I always do hand tight plus an eighth for used spark plugs, hand tight plus a quarter on new.

Cheers,
-Kit
 

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Discussion Starter #5
Kit, When you say fragged, do you mean junked?
I might be lucky not to have done any damage.
 

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The damage would be, if it came out far enough, that the compression would blow the plug out, tearing the thread. Did it screw back in ok? Did you pull it out first and inspect the thread on the plug for evidence of any aluminium?

Its probably ok, just asking...

Cheers,

Roden
 

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Discussion Starter #7
Pulled them all out, cleaned, check gaps and refitted. Threads were all good to my relief. Starts and runs well now.
 

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Yes, fragged as in destroyed. (Etymology- derived from fragmentation grenade.) All as Roden said; if it's good now, it should stay good.

Cheers,
-Kit
 

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Discussion Starter #10
Well it did it again. No 2 plug came out while riding, but lucky I was only 3 minutes from home so I was able to walk home and get the tools to remove the tank etc. Threads looked good, it wound back in easily hand tight and then nipped up as you would expect and starts and runs fine now.

Could it be the plug itself? I'll try swapping them around and keep a regular check on them. But this has got me scratching my head.
 

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Every time when I change the sparks I tight them correctly. After a week or a month after this, every time when I recheck them they are slightly loose. I tight them 1/4 turn more and that's all. No problems after this second check. Some times when I change the sparks I forgot to recheck them, but I have no problem with bike - runs fine and no one spark come loose.
 

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The damage would be, if it came out far enough, that the compression would blow the plug out, tearing the thread.
Loose plugs can also be susceptible to heat damage and break up. We have had a couple of people over on the T3 classics forum who have had plugs disintegrate and do damage to the engine. Not wishing to be alarmist but just wanted to point out that there are other dangers.

If it were me I would get new plugs in there. My personal preference is to fit them at or just below the specified torque rather than use the finger tight plus a nip up method. With the latter I was also lead to understand that you should recheck the plugs for tightness after running up to temperature to ensure they have not loosened. Maybe that would help stop this happening again?
 
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