If everything on the motor is in good order and it still revs too fast ,I sometimes loosen the top plate on the carby and move the plate with the elongated slots then tighten the bolts back up , this gives you a little bit of a change in RPM.
Another quick way is marking the governor shaft and linkage with a texta line or scribe a line on both then loosen the linkage from the shaft and move the linkage so the line doesn't line up any more by 1 mm ,if you go the wrong way the revs will increase so if that happens loosen and turn the opposite way then tighten. You do this a few times until you get the right maximum RPM.
