sounds like fuel shortage ...kinda strange ...settings for the motor should be this
hsn 3-1/2 turns out from bottom
lsn 6-1/2 turns out from bottom
this was determined by screwing the needles in and noting how many full turns it took before the needles bottom out .....this may be the cause as your lsn may be to lean if you are just counterclockwise from flush on the lsn ...i broke my .21 in the other day and thought i needed to lean the lsn from stock to get it running ...WRONG ,,,,,,,had to richen it back up ....