When you removed the old plug did it look like the mixture was rich or lean?

If removing the main jet makes the bike run better something seems to be clogged up in there. With the main jet in try choking it as you apply the throttle, if it doesn't die/ or not as quickly with the choke out, then it I would go back through the carb and reclean it. Make sure to blow compressed air and carb cleaner through all passages and use a small brass wire from a brass brush to clean jets and other passages. Sometimes the gunk in some passages doesn't get completely cleaned out when dipped.

Also, when you put the slide back in make sure the slide and its home are extremely clean. Any oils on there can cause it to hang up on accel. just wipe them off with rubbing alcohol before putting it together.