Motorcycle Questions? Ask a Mechanic.
Hi and thank you for your question.
This is a common problem on bikes that have been sitting. The gas goes bad in the carbs and plugs up the pilot jets. Pilot jets are responsible for supplying fuel at lower throttle openings, after warm up.
The reason it starts ok is you are using the fuel enrichener circuit (choke) which is an alternate fuel supply. Once the bike gets warm, the enrichener circuit supplies too much fuel and needs to be turned off. Your bike is idling high because someone has turned in the idle speed adjuster to attempt to compensate for the no idle condition created by the plugged pilot jets.
The carbs are going to need to be taken off, taken apart, cleaned and inspected, re-installed and synchronized.
Let me know if you want to attempt this and we can go from there.