Engine knock

[outtacontrol11]

Hey everyone, i have a 125c that i just brought. tried to get it running but was way out of time. so i found the guide and sorted that out, but now it has a knock from the top end maybe valve against piston?

The noise goes away after a few secs but sometimes rears its head again.
I was thinking of moving the cam sprocket a tooth or two but should i retard it or advance it? i over thought it and am now confused.
Any help would be great.

 

[sean01]

timing should be set straight up in standard settings...

if it has a bent valve it aint gonna go away by itself lol...

one other thing that can cause a knock is if the cam has the decomp mech and some how isn't working how it should and causing bad rocker clearance every now and then..