Help! my 84 GS has to idle (warm up) for 10 to 15 minutes before its driveable.
 

I have to start the car up and let it idle for 10 to 15 minutes before I can drive it. If I don't do this the car will die when I put it in drive or reverse and hit the gas to move it. I was told previously on here that I needed a carb rebuild. last month I took the carb off and completely dissasembled it. All of the jets were clear, gaskets were good, the accelerator pump was in good working order. It also isn't the timing either, as we have adjusted that. I also know that it isn't the 12a that is the problem. It was pulled from another GS that ran fantastic (even though it was really rough and rusty looking). So does anyone have any suggestions please? Thanks for your time, I appreciate it. -Todd