Poor needle and hot running? Definitely need to disassemble and inspect. Alot of engines I have seen do this ended up having a worn connecting rod. More often than not the exhaust has quite a bit of black residue in it also.

And my experience with Scotch Brite has green as the coarsest with dark red, grey, and then white being the finest. White is so fine it is just about unuseable. I use red and grey the most.