You will have to remove the carbs.
Loosen the clamps where the carbs connect to the rubber boots.
Do not remove the rubber boots from the cylinder head.
Check the float levels, and once you get that done make sure when
you put the float bowls back on that the #2 float bowl tiny o ring is still in place.
Make sure the idle jets are clear.
You can pull them out with pliers, just give 1/2 twist while pulling on them.
Make sure you can see daylight through them. then push them back in and GENTLY tap them down.
Then with the engine off... look into the intakes with a bright flashlight and make
sure that when you turn the throttle that all four carb nozzles are squirting fuel.
Float levels easy check.
Not kidding.
Float should line up with top of idle jet.
On a Roadstar Adventure.