spark plugs blowing

[ghostbiker]

In the last year or so I have had the outside 2 plugs come lose a few times.
They seem to go about 1000-1500 miles ish then I start hearing a little puff piff sort of sound.
Often able to see the cap rattling as well.

When checking they have worked out about half way. Left more often than the right but both do it.
Tried torque settings, tried the normal finger tight + 1/4 and tried very tight lol
Thread from what I can see looks good condition. Plugs have been swapped out twice with new ones and also tried swapping middle ones to outside ones. Nothing makes a diff, about 1000 miles later It's lose again.

So, I don't want to use a thread lock as it probably isn't a good idea on plugs. But anyone have ideas on how to stop it?
Not the end of the world, takes 5 mins to sort each time. But can't be good when its lose

[unfazed]

Did you tighten them with a torque wrench?

[ghostbiker]

Yup, 2nd time they popped out I used one with the manuals settings.

Even had the threads checked at a dealership and they are ment to be fine.

[unfazed]

Were they old plugs retghtened or new ones.
Were they tightened with the engine cold.
A possible cause is dirt lodged under the washer, as the engine heats up the dirt can break down and reducing the torque allowing the plugs to loosen over time.
Noticed it  recenlty on an RSV and it was dirt in the plug seat which had caused it.

[ghostbiker]

First 1 or 2 times maybe. But since then the heads been cleaned with compressed air and also a stick with rag and grease.
As said been 3 plug changes in all so far 1 set of std ngk then 2 sets of iridium.

Totally stumped me and the garage as to what's going on. Threads are clean, whole and look fine. I'm sure they are stretching threads by now but they look fine and tighten up as expected. Just a 1000 or so miles later the start to lossen again.
Why is a mystery, how to stop it is the problem.

[unfazed]

You could try a very thin coat of anti seize compound on the spark plug threads but keep it away from the very end thread to prevent contamination of the tip and  torque them to 13Nm.

[ghostbiker]

I had thought about that, but was worried the heat would just burn off the carrier leaving the copper and lossen the plugs even more. Kinda like the use on the exup bolts.

But I can't see it doing any harm either so with nothing to loose and as the best idea so far LOL will give that a shot later when I stick some more new plugs in

Nice to know my thought train is along the same lines as yours though. Meens I am likely being more logical than I expected I was
Thx

[unfazed]

Your welcome.
Different heat ranges, the head is cooled, but the exhaust is not.
It called thinking out side the box,  :lol 
Here's hoping the RSV I did the plugs on, does not come back with the same problem  :rolleyes

[Capt]

I used to pop out the iridium plugs before each winter storage to put oil in the cylinders, back with the plugs & re torque to spec after fully cleaning out that area, even the seat. Following year outer left plug would always come loose at some point!!