vb20002
those hitachi carbs are funny things and somebody had "adjusted" mine before i got it.
took a while to figure it out.
a few things-
make sure your choke is opening all the way and cable has some slack in it.
make sure linkage is free(not sticking).
you need to identify the idle speed screw, 'cause there is another, that is more accessible, that adjusts some of the choke/butterfly/idle-up linkage relationships.
also check if the idle up pot(increases idle when electrical load is applied) is activated.
mabe none of this made sense unless you have some pictures to look at.
i did an overhaul on mine right away, and that helped me figure out how it works, and i have to put it on every 2 years for smogging.
good luck.