Welcome to the forums, Moro..
I moved your thread to the KTM section where I think you'll get better attention.
Also...as a rule of thumb, do NOT lean your oil to fuel mixture to compensate for rich/lean jetting. Run the premix at the ratio you plan on using.
Here is the proper way to tune your main jet, hope this helps.
http://www.dfn.com/benkaren/plugchop.html