Strange noise from kx125

[Krossipoiss]

Strange ticking from engine.

Hey.
Just did full rebuild to my 87' kx125 and added pro circuit exhaust..
Today i started the engine and there's some strange noise coming from the engine/exhaust..Its like "trtrtrtrtrtrtr"...can't describe it well,but did a video of it..u can hear it strong when i let off the gas...

Uploaded here:
http://www.speedshare.org/download.php?id=91EEC8E811

Can u tell what causes this strange noise?

 

[kx2502009]

sounds like the exhaust is raddling to me but also could be some piston slap

 

[Krossipoiss]

Back from garage...
Tried with original exhaust,still has that ugly ticking...Should i rip cylinder off and look is there all good ?