I'm at my wits end with this problem and looking for experts in these old carbs for suggestions. I know this is long but I'm trying to give as much info to help figure this out. Here is the background. A couple years ago I sent the carb off the J&J Carb in CA for a full restore. Mike at Mike's carb recommended them for a full restore. It came back looking great. I installed it and it ran fine. I had the Pertronix installed about the same time. I had NO issues with acceleration, hesitation or anything, including accelerating up highway hills. Life was good. Then I had the engine trouble and pull it to have rebuilt. When I got it back things were back to normal, until the engine started making noises at 200 miles. Pulled the motor again and the rebuilder found bearing trash and made good on it. But during this process, the carb did sit for several months waiting. When I put everything back in, the engine is now fine with over 500 additional miles on it. But since putting it all back in, I've been fighting this stumbling and hesitation on acceleration, especially when under load likes those same highway hills I had no problem actually accelerating up before. I thought maybe gummed up carb so I ran a can of SeaFoam. Tried premium gas. No help. All fuel lines have been replaced with new ones from Walcks, before this started. Fuel pump is new from before this started. Up to this point, the carb was exactly as when I got it back from the restore and when it was fine. At one point I have verified TDC, and timing at 5 degrees before. I have verified the cap, rotor, wires and coil. It idles as smooth as a kitty purring. I even had the distributor check by a speciality place and they verified all was good as far as bushings, etc., no play at all. They did say the advance springs were very dirty and would stick some, so they were cleaned. I have verified with a timing light that the advance does advance as I rev the engine. I really don't think it's an electrical issue as it idles great and no misses or anything while normal cruising. I don't think it's a vacuum leak as I disconnected everything except the PVC line, which are all new from before this started. It doesn't help, so I eliminated that. I have replaced the carb to manifold gasket, just to be sure. I see no difference. But when I try to accelerate, even from stop, it sputters for a few seconds then gets going. I can run the gears up to 3,000 rpm with no hesitation, other than the initial sputtering. I see no fuel spilling out anywhere. At one point I opened up the carb and saw a little debree at the bottom of the bowl, so I took it apart and cleaned every thing with carb cleaner and assumed that was the issue so added a fuel filter today. I did also discover that the check ball did not have the weight on it. That was the way it was returned from J&J and did work at one point. I've since ordered the full premium kit from Mike's and they told me that the check ball by itself is not right so I added the little weight from their kit today after cleaning everything again. Again assuming the weight and filter would solve it, but it did not. I did also notice that the float was different from the one in their kit. The float I have in, (assuming it was either there originally or put in by J&J), has a sloped bottom on one end. Mike's says that's a float out of a YFA and may work but technically not the correct one. The one in their premium kit that I got does have the correct one which is flat across the bottom. Tomorrow morning I'm gonna change that out and make sure it's level is set right according to Mike's video, but I'm not optimistic that is the issue since the other float was in there when it was working fine. The needle and seat look fine and appear to be working correctly. When it does the stumbling, puffs of dark smoke do come out of the tailpipe, but just when stumbling. That is what leads me to believe it's carb and something possibly with a setting with the accelerator pump. I have checked it and don't see any tears, cracks, etc., but did put the new one in from the Mike's kit. Is there any other settings I'm missing. I've checked and blown out the tubes and jet. Is there some special setting to the metering rod? I'm at a loss and heading to the Coloardo Fall Colors Tour Saturday, so I need to get this figured out quickly. Any and all suggestion appreciated.