Bike runs but wont idle unassisted

I got my bike running last week but now i can only ilde it by gently holding the accelerator, as soon as i let go it stops idling, it was idling unassisted at first. I tried opening the airbox and moving the filter all the way off the box, but it wont idle with that either, even when i use the choke. I thought it was running pretty dry but i got some fire out of the exhaust. Can it refuse to idle if its running too rich, or do i need to tune the carbs? Ive tried almost everything but tuning, including disconnecting the tank and using only whats in the filter but no cigar. Im lost fellas.

 

well , the obvious thing you dont mention is , have you tried to adjust the "idle screw"
you dont mention which bike , but idle screw is usually fitted between the carbs 2 and 3 underneath, you may be able to see it by shining a torch under the carbs, the end of the knob "usually" has notches on it so you can tap it round with a long flat bladed screwdriver

 

Thank you for the insight i have seen the knob, i should have read my manual more. I will definitely try this before i try any tuning.

 

so , working from the R/H side of the bike, tap the notch at the bottom to screw the knob "in" , to increase idle
tap the notch at the top to decrease the idle