2009 YZ450F - Fuel issue (Carb)

Ok so this forum never fails and i have great success with people helping me with my bike. so this is my last resort before i rip the bike apart and look for the problem.

So, i have taken my bike to 3 dirt bike/racing shops and they all wash their hands of the problem. They say they have a pro rider and he said there is nothing wrong with the bike.

Here's the problem: First of all when the bike is cold, it is hard to start, takes maybe 8 kicks or so with the choke out. when I get the bike running with the choke out it runs ok but as soon as the choke is pushed in it idles real low and eventually quits. when i get the bike in gear and ride it, it coughs, spits and stutters as well as the exhaust pops like crazy. I'm not sure if it needs a carb clean or some jets replaced but i was hoping i could get some input here. I was told by a mechanic that the needle and seat but I'm not sure if that is right.

Any input is greatly appreciated. Thanks.