I agree with 51 woodie, that Muriatic acid works great to clean the Small
amount of aluminum from the steel cyl walls of small engines.
I would like to say, do NOT use Muriatic acid to clean aluminum.
I put a small aluminum part in a quart can of Muriatic acid to clean the part.
Very quickly, the acid started eating the aluminum and filled the room with
smoke.
I had to get out of there, as it was like
Tear Gas and burned the eyes to the
point that I had to feel my way to get out of the room.
So be careful, that NO aluminum is on the part you want to clean...
.