Hey.

I bought an used rally 300 rider with only 500 on the meter. The last owner bought it new and got bored with it so it has been standing in a warm garage for 6 years now until i managed to buy it and bring it home. I was on my way to fill the tank until it stalled on me! Im pretty sure i just ran out of gas and i went and filled up the tank. Now it wont start/idle. If i spray some carb cleaner in to the airfilter box and start it up it runs fine on higher rpm and rides fine but once you let it idle it stalls. I found also this mystery brass slide on the carb that i pressed in and cannot get out. What might the slide do? I will link a picture of the carb and slide. I have cleaned the carb and have new plugs.

Brass "slide" that was out like 1inc before pushed in 🤭

 

Your idle jet or passageways to it probably are still partly blocked. When you run out of fuel, you pull dirt, from the bottom of the tank, through into the carb. I'm not familiar with that bike or it's carb. The brass things may just be blanking plugs for the internal passageways, strange they would make them too long and sticking out though.