Given the low hours on your machine the following bits probably don't apply:
1.Bing carb slides are prone to wear,and when they wear people will compensate by bumping up the pilot jet size - it doesn't work.
2.When the needle and seat assy. start to wear (or your float height is too high) you'll feel it first off the bottom.
3.Over oiled air filter.My 380 tells me it wants the air filter cleaned when it starts to get a little rich off the bottom.
When you initially crack that throttle (when the slide starts to move) you have three circuits at play,you are transitioning from the idle air circuit, you are in the "meat of the pilot circuit and you are transitioning to the slide/needle circuit.
I recently resurrected an old Sachs that had been ported and had an aftermarket pipe.I installed a Mikuni round slide and proceeded to get the jetting sorted out. After numerous pilot/air screw combinations and after going to a more slender needle(more gradual taper) and shimming the needle I still had a "hitch" right off the bottom when I first cracked the throttle.At this point I remembered an old trick taught to me and I "cheated".I took .020" off the intake/bevelled side of the slide.
After that the Sachs ran "electric" most of the time,the hitch only reappearing slightly when the motor got hot.At that point the bike was a first kick starter so I didn't worry about it.
