Dt125r making noises in high rpm

[Bananper]

When i am riding my bike and it gets warmed up good, it starts making these ugly noises in high rpm, and they keep getting worse as the rpm goes up. I have ridden the bike for a couple of months now since the cylinder was honed and i put a new piston in it. There is no drop in power or compression. Almost sounds like ignition knocking at some point

[Calum]

What's the spark plug saying. Could be detonating?

Check the colour of the plug.

Was the barrel rebored? Is the YPVS fouling the piston. has the YPVS been installed the right way. Is it rotating the right way.

Is the exhaust blowing?

[Bananper]

@Calum everything seems to be right. Ypvs works. I pulled out the plug yesterday, on the end of the ground electrode there were a small bit of carbon, i thought that was causing the problem. I swapped the plug, and same thing happens when the bike gets hot. Could it be pre ignition? I've read that carbon deposits on the piston could cause pre ignition when the bike heats up.