Boots might be fine, but how bout the gaskets on the reed cage? Start the bike, let it idle, and spray all around the boots, reeds, cylinder base, carb, etc. with starting fluid. If idle fluctuates, you have a leaning condition.
When it starts to do this, cut the engine ( Kill switch ) while it is running at full RPM. Pull the plug immediately and see if it is leaning (White-ish coloration of the ceramic portion of the plug)
Be careful cause 1, it is NOT safe. And 2, if it is leaning, your gonna have it let loose on you sooner or later and be doing top, and bottom possibly, rebuild.