Re: 1st gear stumbling
I think I had the same problem as you.
Do you feel like the engine surges (you feel like a dead spot) when you let the clutch out, but its not the engine that misses? It's probably your clutch. Try letting the clutch out slower than usual. Did it help any? If it did, its probably something that is warped/worn on your clutch.
I had the same problem, engine and carb were fine except it felt like the CJ had some sort of "flat spot" when I started from first. Did not have any problems in any other gear or speed. I replaced the pressure plate, friction disc, throw-out bearing, and pilot bearing. I also had the flywheel resurfaced. This cured my problem.
Like it was mentioned above, make sure the clutch is adjusted properly and make sure your carb is running fine and its not causing your engine to really have a flat/dead spot.