“I hear lots of complaints about the 4300 - what were it’s weaknesses?”
Cali, I have not had all of the reported issues but I will report what I have seen.
Starting with hesitation off the line. Accelerator pump on the 4300 is a spring loaded polymer(material ?) cup piston. The piston cup would have issues either from wear or getting cut upon assembly, or, alcohol poisoning. I found the later on mine but also found the the check valve breather (on older 4300’s) would allow gas to shoot upwards out of that breather vent. So accelerator pump is a complaint, I was able to fix these two issues in my case.
Another common complaint that I read about was the various mating surfaces of the 3 piece body would warp and leak. I am fortunate to have a machine shop where I was able to inspect mine on both carbs now and subsequently repair the small amount of warp that I found.
Adjusting the float for the auxiliary valve and the primary valve is a common complaint area but I have found, in my case, that if you follow the shop manual on this there are no issues. Many people get rid of the aux. valve, I’m currently using mine but soldered the aux. valve closed on the old 4300. On the old 4300 I saw no difference with the aux. valve blocked. The old floats reportedly had some issues with whatever poly-raz-mataz material they were made from. New ones seem fine.
They are a pain to work on in the car like RB reports above. And he is right about getting the top off in the car but it can be done and you must be careful.
If you are seeing sediment in the bowls or else where I would look into that myself. I am no expert and there are other complaints, this is what I have seen.
As an update to my original posting, I have procured a proper 4300 and rebuilt it. It is in Pole Cat but I have not been able to play very much, but at first glance, I will just say my burnouts are twice as long. First jetting was lean and all it has done around here since is rain when I can play. I will be restoring this carb over the winter. Probably going to try some DIY plating here at the shop.
Stay Safe out there,
Gary