I'm going to change my vote from someone else doing the work to ME doing ALL the work so I TOO sound like I'm a wrench!.....
One of my yz490's, I busted 3 gear in a race, took the whole bike apart including the case, been sitting around awhile and a move, putting it back together is going to be fun.
I used to do rings, pistons, primary chains and more on my old Maicos because they certainly needed all that. As I have gotten a bit older and wiser, I think today's bikes are far more tricky for my patience and desire. I change my oil and filters, clean the air filters, change the sprockets and keep them clean but if anything else comes along I take it to the one's who I trust. Have not had to do this in a long time however.
Sounds like there are one or more blocked jets.I'm guessing the pilot or slow jet might have some crap in it.My XR350 had a similar prob,ended up removing the carbs & dis-assembling both(one at a time),spraying carb cleaner into every tiny orifice & passageway then blowing it out with a shot of air.After that it started on the second kick & idled great but died when I gave it full throttle...ended up being the float level on the secondary carb(too low & no gas in bowl).My wifes 660 Raptor (I know...) She's uses all gears but only half the throttle (if that)...It sat for too long and now (I think) has carborator issues...it backfires every time you gas it. I tried mixing some cleaner in the gas AND squirting some directly into the carbs but to no avail. Dual carbs...looks like a real PITA...anyone have experience with these?