So, let's talk about how it runs with the chain removed then. Does it jump like a chainsaw should when you touch the throttle, and does it idle steadily for a good while? The reason I ask, is that you can get the carburetor right but have a loose cylinder base leaking air, or a leak between the crankcase halves, which results in weak crankcase compression. This causes very poor running especially at low speed and light throttle. One of the signs I've found that point toward leakage, is needing to use the choke to restart the engine when it has only been stopped for a couple of minutes.
