125-200cc 125SM spark plug

Hello.

I have a 2003 Husqvarna with following settings.

Custom pipe
Vhm top
35mm mikuni tmx ( 35 pilot! 330 main, 2 hole needle
4% fuel pre-mix

My spark plug looks as the attached image, what can be wrong?

Well I'm no spark plug mechanic but it looks rich to me. May need better fuel and mix since it seems you have a hp head setup. Or, order the Lectron and look for improvement.

What is the Lectron?

And how is my fuel mix bad? Should I run 2%?

Higher octane than reg pump gas with a faster burn rate and a premium synthetic 2 stroke oil which will provide a cleaner burn.
The Lectron is a metering carburator that can be dialed to the desired richness of fuel delivery and provides better atomization, resulting in less unburnt fuel.

Saborthooth is right that plug says its too rich, do you get any flat spots in the rev range when rolling on the throttle from certain points?

What does flat spots mean? I don't think so! It pulls fine from 0 to 100 km/h.

And if it was possible, I would try not to buy a new carb.

I am using Castrol Racing A747 as two stroke oil.

Sorry fella, does it hold back at all even briefly ? if it does as say anywhere from closed throttle to wide open it can tell you what jets to change to stop it from running rich

No it does not have any flat spots, I will try 2% mix in 99 octane tomorrow.