As far as I know (I think), that engine has a black plastic "limiter" on the high end speed needle. Remove that part.
Now start the engine again, SLOWLY rev up to full throttle and adjust the high end needle for optimum speed, then back off 250 rpm (if you have an rpm meter), or three clicks. Lower the throttle and then SLOWLY rev up again.
Will the engine idle OK and then come up to speed OK ? If satisfied, put engine from full throttle, back to idle. Now quickly rev up to half speed (goose it). Does the engine rev OK, without hick-ups ? If yes, you're done, if not, you have to adjust the low end speed needle (the one inside the throttle arm). Adjust in VERY SMALL increments, until the engine will smoothly rev up without hesitations. When satisfied, one more last check. Slowly rev up, then lower back to idle. Pick up the plane and hold the nose up 20 degrees and then lower the nose 20 degrees. The engine should not die on you. If it does, the low end needle is still not at optimimum. Continue until all parts of the tests are satisfactory.

HTH.