There are a few parts I painted on my bike that where previosly chrome.
A front air dam and the rear light bar to name a couple.
I first sandblasted the chrome and removed the smooth surface,then I primered the parts with a self etching primer.
Then I painted them with an automotive urethane paint.On the rear light bar I used vinyle pinstripes to macth the bikes and cleared over them.
The match is perfect,and the parts have held up great for five years now.Even behind the front tire.
Here are a couple pics that show the parts.
With the aluminum engine parts,if you cant blast,use a good paint stripper to get the existing clear off,then sand with 400 grit to etch the surface and follow up with a good self etching primer.You can get this in an aeresol if you do not have air.
Also.if no air,you can use VHTs ,DUPLI-COLORs or similer engine paint witch you can get in glossy or semi gloss black.Ive had good luck with these paints especially if you throw them in a toaster oven at 200 degrees to cure it.
Just a side note,the DUPLI COLOR semi gloss engine paint is a perfect shade for parts like gauge bezels and such where a high gloss just isnt right.