There are two things you can do to attempt to improve performance without taking the carbs or engine apart.

First, you may have clogged carb jets and other parts gummed up.  If the bike will start and run, try using Berryman B-12 carb and jet cleaner.  Pour half a can of the liquid B-12 into an almost empty gas tank and fill with 87 octane.  Run the bike until the tank is almost empty and pour the rest of the can into your tank, fill again, and run out the tank. This should remove any gum and small blockages in the fuel system.

Next, if necessary, do the same empty tank procedure, but use Seafoam or any other motorcycle combustion chamber carbon removal liquid.  The BUBF's can and will carbon up the piston crowns, heads, and valves.  Seafoam can also be sprayed into the carb's intake w=while the bike is running, but be ready for a lot of smoke.  The engine will slow so keep rolling the throttle to keep the engine running.  Some BUBF owners have had good results de-carboning the combustion chamber spraying plain water into the carb intakes.  This will cause far less smoke, cost a bit less, but you will still need to roll the throttle to keep the engine form stalling.