This symptom can be caused by normal vibration. Check that the muffler is affixed tightly to the engine, and that the muffler halves are not loose.
Cheers,
This symptom can be caused by normal vibration. Check that the muffler is affixed tightly to the engine, and that the muffler halves are not loose.
Cheers,
That is caused by some aluminum (usually the muffler) vibrating/rubbing somewhere. The black stuff is actually the very fine aluminum grit or cast-off in the exhaust. It is NOT caused by any break down in the running gear of the engine, that is, the piston, connecting rod, or crankshaft as there is no pure aluminum there. Tighten up everything and the problem will go away.
Yes, a loose muffler can cause dark oil, but there are also other possibilities, such as fuel.
After running many gallons of CoolPower through my Super Tigre G.61 I switched to another brand of fuel and immediately started getting a dark oil collection on the tail. When I switched back to my previous brand of fuel, the symptoms went away. When I took a gander at the internals, there was very noticeable wear to the cylinder.
Try a different fuel brand and see what happens.
Dave
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