PaulR is correct and to add to that my question is have you made any linkage adjustments?
Your engine advances timing when you move the throttle/fast idle lever first before it actually moves the throttle plate to add fuel.. So before we add more fuel we actually add more timing and that is what initially increases rpm.
Setting this up is called sync and link. Its very critical to the performance of your engine.
You need to qualify your ignition system. Do a simple spark test with a sealed spark tester..
If spark is good then install the proper spark plugs and when running do a drop cylinder test by using a insulated pair of plug wire pliers or suitable one's that will work and remove one plug at a time and if there is a change in sound you know that cylinder is working. If no change then you have a starting point.
If its all good.. go back to those carbs..
Did you clean the carb in a vibrasonic? Did you install a new carb kit? needle and seat?
Best of Luck
