There are several methods for cleaning aluminium but the chemical ones are fraught with difficulty. I suggest you look at this:
http://www.enginebuildermag.com/Article/2601/cleaning_aluminum.aspxThe central theme is heating the parts to a maximum of 250 degrees C (preferably a bit less, but that is the maximum that won't ruin the casting) for some hours, to bake the oil out of the crud, then more or less dust the loose dried crud off. However if the aluminium itself is oxidised (metal surface itself is discoloured from extreme heat) it may still require glass bead blasting, or manual scraping, after it is cooked.
This thread should be in Repairs and Maintenance/Questions on Engines/Questions on Victa 2 Stroke Engines, Blumbly. There are getting to be a lot of forums, but they are not yet fully set up with their new structure. Hopefully people will find it easier to navigate than it was before, when it is finished. The idea is to have "a place for everything and everything in its place", so you won't have to wander around trying to find things. I'll now attempt to move this to the correct forum.
