CRF 450R 2008 carb and engine backfire.

Hi' i've just finished rebuilding my 08' CRF 450R, and i've encountered first issue, at first i even had problems starting it, but after messing with throttle a little i managed to get it running, but it bogs at lower rpm, doesn't hold steady idle, and consistently backfires through the carburetor (and generates white smoke), also it gets hot quick, and sometimes backfires through the exhaust, though these are "dry backfires", no actual fire comes out of the exhaust. Here's a video of it running: https://youtube.com/shorts/-vXGbukR43w this rattling sound is backfires hitting the throttle, and before you say it, i know that it got hot because there are no cooling hoses, but i took this video before installing the cooling system, even after pouring in coolant it still got hot fast. I turned AFR screw 3 times (for crf 450 it's too much) and it still runs lean.
Here's some additional info:
-Intake valves are freshly replaced, but they are slightly out of spec
-Ex. valves are good
-Carb has been sitting for 2 months before first start but jets are clean (though im not sure about idle jet or whatever you call it)
-I've seen some guys mentioning it, my elevation is 400 meteres above the sea level
-Spark plug is not the freshest but it's still in good shape
-All timing marks are aligned
-And tensioner works good
I have no idea what to do honestly. I'd be glad if someone could help me