Demon Carburetor issue

Have you ever had the carb apart? The Demons were notorious for having machined metal shavings in them. They can be excellent carbs, but the quality control sucked. If it was mine, I would strip it, soak it in cleaner, blow it out vigorously with HIGH PSI compressed air and build it. It almost sounds like maybe the vacuum secondaries are opening too soon and drowning the carb with air. If it does the same thing after the rebuild, maybe adjust the secondary opening.