I am going to first try vinegar this weekend. I am going to put in in a spray bottle and use a toothbrush to work it in then hose it off with my garden hose (cool motor of course). I will post before and after pictures so you can see how well vinegar worked.

Weather permitting of course, I live in Washington and it has done nothing but rain and freeze over in the past few weeks.

Thanks guys for the help!

 

Acetic acid, ascorbic acid and vinegar and even possibly unsweetened Kool-Aid seems reasonable. In the Navy years ago we used ascorbic acid to clean brass steam lines. This method required heat i.e- allowing the water to boil for several minutes.
Think I'd try the vinegar first on a hot engine wrapped with vinegar soaked towels .
Since we are talking about aluminum and not brass, theres no guarantee so start slowly with this idea.

 

wd40