I spent many hours in the last few days playing with both needles
(with help from some fliers). but is seems that nothing won't stop the engine from rocking starting at about 3300 rpm.
can it be some structural damage (like unbalanced shaft ?)

i must admit that this is my first 4 stroke engine so it's hard for me to determine whether this problem is caused by some wrong tuning or some big structural damaged.

thanks