Some oil remains unburnt in a 2 stroke and condenses in the exhaust. Is there a lot of oil in the muffler? Isn't your bike brand new? Are you running an oil rich break-in mix? What does the spark plug look like? Oily?
its 25:1 it was in the manual to break in and run it on 25:1....its not a whole lot but enough that i notice and yes its new but i ride it alot...the oil i put in is blue and when it comes out its grey/black..im guessin this is the carbon?...the spark plug has a small amount of brown residue on it kinda on the threads...i just need to know cuz i have 2 more weeks onm the warranty and dont know if i shpuld send bacjk....
as mickey indicates depending on the engine make, between 5% and 30% of the fuel goes straight through a 2-stroke engine without being burnt.
Some of the oil will condense in the muffler, as it cools down.
Oil molecules are larger and heavier than gasoline molecules, and so, they will condense at higher temps, and will not easily evaporate, as the gasoline will. (This difference in condensation temperatures is how the oil companies separate crude oil into it's components in a distillation tower at the refinery.) In your case, the oil condenses out in the muffler, while the gasoline goes on through.
A small amount of oil is normal.
The reason that it is black is because of the carbon. The dye, which caused it to be blue, was probably burnt & broken into carbon also.
One of my HT engines will drip from the exhaust and one doesn't....I asked Duane at Dax what might be the cause and he suggested that my float may be hanging up and letting a minute amount of fuel through the engine when it is off....I disassembled the carb to make sure the float moves freely.....now no more problems!....(when it was a problem I used to put a tin can under the exhaust to catch the drips....not a lot granted but enough to make a little mess over time....If your carb doesn't have a sticky float I would guess the above posts would likely be the answer to your problems.
I would guess that it would depend somewhat on driving habits, too. If you take the bike on a lot of short trips, the exhaust may rarely get hot enough for long enough to burn out all the residual oil.