Long story short...

Atv was given to me recently by relative, only had been ridden a few times since new and sat for 9 years. Carb and tank was gummed up with old fuel so I cleaned out the tank with acetone and put put a new carb kit in.

I turned the mixture screw on the bottom of the carb out 3 turns and it will start and warm up with the choke on but stall once the choke is turned off.

If I cover the intake with a rag it will run without choke but rev near redline and will stall once the rag is removed. I made sure that the clamps on the intake boots were tight and the air cleaner cover was on correctly.

Doesn't this sound like a vacuum leak? Where could one even be?

 

Could be the inlet manifold split, I believe Yams are prone to it, but it sounds like dirt in the carb, or a wrong jet. I never fit carb kits. If something is wrong with a carb, like a leaky float needle, I clean it, check for faults and only change it if something is wrong with it. You can end up with more problems by fitting wrong or badly made parts from a kit than you had in the first place.