I have an 01 banshee, I am a new 2 strokes. What could cause oil to leak from mufflers? Only power loss is in the bottom end.

 

Rings could be shot. Time for a compression test. Could have oil/fuel ratio on the rich side.

 

Two Cycle engines depend on top and bottom end compression, also back pressure!
Correct Oil to Gas ratio is also important.
If a 2 cyc engine gets loaded up and then sits for a while the inside of the muffler gets a tar like residue that will not blow out, usually it is at the tail end ot the exaust. This creates a snowball affect every time it is used after this point.
If you look at the spark plug it will look very dark sign that it is running rich caused by the increase of back pressure due to this buildup..
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If there is packing used in the exaust remove it and wash the unit out and then replace with new packing!
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I remember the old 2 cycle 175cc the baffles were removable and you had to actually burn off this tar like buildup spray carb cleaner on them and light them up or bake then on the barbaque until they are dry.
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Also if the baffles can not be removed take the exaust system off, plug up one end with a rubber stopper and pore Easy-Off oven cleaner or lye or liguid plummer let it sit for an hour or two to get that tar desolved then flush it with a pressure washer.
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Be carefull in all cases not to get that pushed in you face or on your skin wear goggles or a face mask to be safe