I know there a few here who are restoring and cleaning up their scoots. I ran across this website with some small brushes for precision removal of corrosion and dirt from cast aluminum alloy motorcycle engines. http://www.machinerycleanery.com/index.htm
These are pricey, and beyond the needs and wants of most of us I think.
However, here`s the source if you really need a tool like this.
Edit: Opps, reversed the name of the company in the thread title.
Should be Machinery Cleanery.
1991 VN 750 -"Cosmic Lady" or "Bad Girl"?
Purchased May 16, 2008
Approx.19,300km (12,000 miles)
Fiamm Freeway Blaster horns
F&S luggage rack and engine guard
Kury Offset Hiway pegs
July 13, 2016, Riding on the DARKSIDE now, Classic Radial 165/80-15