How to clean Oxidised engine cases??

[Brockett]

My son (42) and on the big side, has aquired an 08 Honda Varadero 125 in order to get back onto a motorcycle. The bike had done about 13000 miles in 13 years and, as I supected when I saw it, has spent more time in a shed than on the road. The engine crank / main cases are in need of a clean up. the outer cases are not too bad but the inner case is a bit furry.  Does anyone know of a method / product that will sort out this issue. And what the best way to protect it. All this without removing the engine.

[Mr Nick]

Some of the alloy wheel cleaners are useful at getting the fluffy oxidation off: it's the ones with the most warnings that you're after as they contain the good stuff.

About your only option in place is a rattle can paint job - protect the bits you don't want sprayed as best you can (or as much as you can be bothered). Other than that, you could just resort to dosing it all with some oily rust prevention potion but a layer of paint is better at keeping the water away from the alloy in the first place.