Forum bmwbike.com

The exterior of R60-2 engine was in a fire and requires cleaning to bring back the glow in the surface. I have tried Alum. Jelly which is phosphoric acid suspended in gel, with limited sucsess. Any other ideas short of glass beading?

I have had good luck with a commercial product known as Simple Green and a stainless steel brush that is slightly larger than a tooth brush. Slow circular motions with a spray bottle of water near by to wash away the crud. good luck.

Phosphoric acid is probably the most powerful chemical cleaner for aluminum. Some people have had success mixing the acid in a very diluted solution.

I used the acid in the form of a commercial mag wheel cleaner, one of those spray bottles. Someone recommended Eagle One Acid Etching Cleaner from an auto parts store. I don't know if I found that one or not. I sprayed it on my final drive which I had removed from the bike. The cleaner foamed up in a satisfying manner, but then left the casting black. So I bead blasted the final drive which of course made it look perfect. After that experience, I will not use phosporic acid again.

Mar Huggett has recommended the use of bathroom scouring powder in this forum:
"...Chemical cleaning as never been my favourite as irrespective if the chemicals are acidic or alkaline, it is extremely difficult to neutralise the aluminium. If the aluminium is not neutralised, it can start to discolour and shows signs of efflorescence (leaching out of salts on to the surface). In addition, the chemicals do not remove the deep ingrained dirt very well. If you cannot blast the housing, then only painstaking scrubbing with an abrasive cleaner (my favourite is still the old fashioned VIM for bath tubs) with help. "

Someone else also recommends scouring powder, and also cautions against the use of steel wool:
"For the last 30 years part of the way I make my living requires cleaning and polishing stainless steel products. In my early years we used steel wool and various metal polishes. This process left an excellent finish that our customers loved. Within a matter of months our customers would call to complain about our cheap stainless steel rusting. On our return trip we found the stainless steel covered with small rust spots. Examining the Stainless under a microscope revealed steel wool fibers had become imbedded in the stainless during our cleaning process. Exposure to the elements would wash off our preserving oils (WD40) allowing the steel wool fibers to rust.
Steel wool fibers will become imbedded in aluminum much easier than they will in stainless. Today we use Scotch Brite pads on both stainless and aluminum. When we want to clean but not polish aluminum we use a heavy bristle brush and Bon Ami cleaner. Bon Ami gets everything out of the pores but does not alter an "as cast" finish. Any Bon Ami residue can easily be washed off with water.
In a bike show WD40 adds a nice luster to "as cast" aluminum. If you ride a bike with WD40 on the cases you end up with a bike that gets very dirty very fast."

Based on all this, for normal cleaning, I would use scouring powder with either a Scotch Brite pad or a fine brass brush, rinsed with water and a scrub brush, and then protected with WD-40. For regular washing I would use S-100 Cycle Cleaner or its cheaper generic cousin Simple Green, followed by WD-40.

However, since your engine has been in a fire, the metal may require bead blasting to remove its discoloration.

Dear Bob:need to know the proportion about phosphoric acid suspended in gel (What type of gel? ).
What about robber parts and gasket ?
thank you