dark liquid dripping out of muffler

If you have a 2 stroke engine, you didn't tell us, yes, oil from the muffler is normal. The oil in your fuel mix, for the most part, doesn't get burned and has to go somewhere. It ends up as oil vapor that leaves the engine in the exhaust.
Using too much oil will make this problem worse. We recommend no more than a 24:1 mix and preferably 32:1 after break in.
Tom