As mentioned above a couple of times, please check the "link and sync" of your carb to magneto timing, it can really make a difference and can make a motor act like yours is acting, at least in my experience.

To do this, look on the front of your mag plate, and there should be a triangle wedge bolted to the front of it. It’s the one the carb linkage roller rolls on to and fro when you open/close the throttle. It’s right above your carb.

There is a mark on the triangle piece. It needs to be timed so that the roller is on top of the mark just as your LOWER carb linkage starts to move. It’s the linkage that is connected to the horizonal throttle shaft that goes thru your carb.

There are two 5’16" little bolts under the wedge. Loosen both slightly and move the wedge in/out as needed to get the timing right. One bolt is in a round hole, the other in an elongated hole to create a pivot point and a tightening (set) point. It will take a few setting and tightening tries to get the timing right on.

You can clip something like a alligator (roach) clip onto the actual throttle shaft on your carb for an observation point to make it a little easier to see the carb shaft move to set it to when the roller just reaches the line on the wedge.

If you have any trouble doing this, post back and maybe someone can explain it better.

Check this first before doing anything else… Just like a car or anything else, it needs to be timed correctly to run correctly.