Need help on engine noise?

[Stabler]

Hi gang.

So I have a distinct noise coming from my enginge when I "coast". I can't hear it at idle or when I rev up or when I accelerate away. Just when I've reached my speed and keeps it there. Then I hear a distinct "clonking" or almost a banging. Not like hitting metal with your hammer, but still.
Also the sound isn't on every stroke, it's irregular, but never more then 2 seconds apart. And it comes a couple of clonks/bangs at the time..

I first thought it was my tank coming loose, but it wasn't. It's definitely comming from the engine.

I've pulled my plugs and they both look like this:

I've also noticed a "sweating" around the cylinder head like this on both sides:

Now it also have difficulties getting back to idle after I've been riding down the street and back. (I know this most likely is an air leak, but my intake manifolds are brand spanking new, and it doesn't explain the clonkig/banging).


So to sum up, my question is, does anyone have an idea as of what this could be?
All ideas and pointers would be widely appreciated!

Thanks, Stabler.

 

[Stabler]

And I don't know if I'm imaginig this but I can maybe feel those clonks/banga in lack of power in the bike..
Could this be due to a burnt coil?

 

[drewpy]

checked the front sprocket on tight?

chain loose, and it bangs on the sprocket cover?

 

[Stabler]

Damn. Perceptive there drewpy! I'll check that first. Don't think I have to much slack on the chain though, but I'll check.

Thanks!

 

[Stabler]

Drewpy - your spot on here. Loose chain bangin' on my rear fender. Do I feel stupid? Yes.
Thanks man!

 

[xschris]

Just be happy it stayed on

 

[drewpy]

yep, glad it was done sooner rather than later.

glad to help a swede out

 

[Stabler]

Yeah. Thanks! Now I just have to find the air leak. Shouldn't be to difficult.