Best way to clean...

Hey, is there a way to clean this part of the metal? (surrounded in red)
its really dirty!! try to clean it as well as I can but its hard to get to, and cant believe its got to how it is to be honest.

Toothbrush and elbow grease!

Spray the area with a degreaser, WD40 works well. After cleaned and dry use an anti-corrosion spray to protect it, ACF-50 is really good.

If that's the actual engine case (?) then wire brush ftw

I usually spray WD40 anyway which I thought would of worked, what anti-corrosion spray would you recommend?

Its this part of the Bike:

wire brush it till it is shiny as f**k, the use autosol chrome and metal polish and a clean duster to make it gleam

Its getting there... some bits are really tricky to get in to!