Same here as MD and 2LZ. Properly oil filter will keep the dust out. My bike is quickly approaching the 6000 mile mark. I stuck my bore scope in over the weekend just to check things out. I still see cross hatch on the cylinder walls. Still has good compression as in no loss of. I have been running synthetic ever since my initial break-in. Approx. 800 miles.
Glad to see you got her fixed up.
Gotta love these low cost bikes. Try fixing a Jap bike for that cost. lol