Just bought a 1990 Softail Custom with a Keihnin (Screamin' Eagle) butterfly carb and drag pipes. It ran good for the previous owner (known to me and trusted) but wasn't used much in the last two years. It will stumble and pop back through the carb for about three miles almost without fail, then run smooth until it's shut down and cools off. A new carb kit didn't do anything for it. Any thoughts on why it only wants to run right when warm?

 

Does it do it when you use the enrichener (choke)?