hi!
just got a gt80, first bike, i dont know much about mechanic stuff on these yet.
i can't get it to idle well. just rebuilt the carb but it's still not doing it... if I don't give any gas it'll just cut out—makes stop lights a nightmare! what do you think my checklist should be?

Hi & welcome from NZ.
Not easy to say what the issue could be. How does it feel for compression on the kick start.
Should have a reasonable bump not just a soft resistance like--umm--running a knife through very soft butter [first thing i thought of haha].
Secondly people say Rebuilt the Carb but often that opens a can of worms.
There's a tiny little idle mixture jet that you really need to remove & look through-poke clean- but its So Small.
Idle mixture screw is usually about 1.5 turns out from seated, but if you screw the Speed Screw up a bit to Try & hold an idle of sorts, then adjust the mixture you should observe a difference--in for rich & out for lean, so in might richen to the point of stopping the motor.
Out would get to the point of fading away-lean & wanting to stop.
So find the ideal spot which as i say is about 1.5 everything working as it should in a good motor.
Stuff like that. Good idea to run a video if ya can so we can hear whats going on just sitting stationary not on the road as such. I'm just wild guessing to kick things off.
Crank seals are a possibility or on the mag

One more thought though. Is it a lever type choke & are you flicking the lever up for normal running.
If it's a pull out knob the push in for normal running.
Regarding the idle mixture screw i hope the carb isn't one of those with a blanked off screw [like my chainsaw] as US models do stuff like that on some bikes but maybe not as early as your model.
Mixture screw will be on a steep angle & speed screw will be straight in [lifts the slide a little].