The slide should not spin in the carb body.
If you get the slide lined up properly and set the idle gap. Also have the needles reset to factory break-in settings. you'll need to rebreak-in the engine. Sometimes the engines do start hard when fresh and tight. Are you sure you have the piston and sleeve installed corectly?
Spitting small ammounts of fuel up out of the carb is normal for some engines at idle. It's because of the crank port timing. If it's spitting lots of fuel out of the carb I would look to see if the piston and sleeve are installed properly and that the engine is rotating the correct direction.