Engine click click

Hello,
i'm always looking for my engine noise ; click click.

I checked all :
It's not the timing
it's not the exhaust
It's not the chain tensionner.

But finally an idea !
Last year i make rebuild the spark plug hole. But the new filter don't do totally inside and i have perhaps a 1 mm edge under the spark plug.
So the spark plug is more short than other one inside the engine...

and i find this tonight :Can bad spark plugs make noise?  Engine Knocking

That sound is caused by your spark plugs not detonating properly and igniting all the fuel. The fuel and vapor that did not ignite eventually will catch fire and detonate. When that happens, you hear a knocking sound from your engine. Bad spark plugs are common causes of engine knock, but simple to fix



so here is my question :

what can i do now to resolve this ?

1° bend the spark plug gap more than other ones ?
2° going more tight on the shims (a more big shim but i'm actually on specs) ?
3° remove the "ring gasket" of this spark plug ?
4° try a more long spark plug ?

What is be the way ?

Regards
F

Not sure what exact repair changed on the head , But proper fix is to  make the hole to correct  specs, so it matches other 3 cylinders 
Anything else is marginal and  is a severe  compromise
Dave

Personally I would remove whatever has been done previously and use a " time sert" to bring it back to correct spec (this also gives a good surface for the seal

 

This is the time insert actually on the head. You can see the edge on the top of it. The engineer was not able to fit it inside totally...
I think i will play with the gap today and see if the noise is the same ot not.
For the moment i want to know if that is the problem...

wrote:

This is the time insert actually on the head. You can see the edge on the top of it. The engineer was not able to fit it inside totally...
I think i will play with the gap today and see if the noise is the same ot not.
For the moment i want to know if that is the problem...

Any exposed threads below the sparkplug , or any metal protuding into the combustion chamber will cause a hot spot which can cause   pre ignition / detonation 
Dave

The "time sent" should be flush with the base material (see the green part in the diagram) if it's protruding it sounds like it hasn't been done correctly. Was it done with the head on the bike (where did the debris from drilling and cutting go ?) and as Dirk said, are you sure it's not poking inside. This sort of work should always be done with the head removed as there is always "debris" and as it's alloy you can't recover it with a magnet

 

How to repair a spark plug thread with a Würth Time Sert insert.

kzrider.com/forum/2-engine/617634-spark-...hread-repair?start=0