Today I took the jug and cylinder head into work so I could clean everything and get the jug ready to ship out for bore/hone. I used the parts washer and noticed that the dirt seems to be baked on to the aluminum. Anybody have any tricks on how to remove this stuff?? It'd be nice to bring it back to it's natural aluminum finish. We use a standard mineral spirit solvent in our parts washers. That, and carb cleaner had no effect on the mess.