+1 and 3/4 to the above,
if the bike, or any vehicle for that matter is driven easily for normal commuting, and then gets to stretch it's legs, the carbon will build up inside the pipes, the extra vibration and velocity will loosen it, and will burn back off. I'f you are truly worried about burn off of another kind, check the coolant, and oil, the two should not mix... if a gasket is leaking, then coolant will burn through the engine. Probably nothing to be concerned about hopefully.
Take a Garden hose, and force some water down each pipe,, roughly a half gallon will do, then crank it, and spew it all out!! that should clean it up! makes a cool spray...
LOL Just kidding,, don't do that... real bad