Greetings from Beautiful N/E Georgia. Hope all is well on your end of the wireless.
We've "blacked-out" several 'scooters at the shop. We start by bead-blasting the parts. If they're made of aluminum (motor/trans cases/covers, breathers, lower legs, hubs) we clean them with aluminum wheel cleaner. We wash the steel parts with Dawn dish washing soap & blow dry them. Next we prime them. We use gray primer on the steel parts. The aluminum parts are primed with "self etching" primer.
Then, paint them. We've done mostly black (gloss & satin finish), did one in red to match the paint on the sheet metal. They've all turned out real nice.
The first one we did this way is a '95 Sportster with a 88 c.i. motor that gets ridden hard nearly every day. We did that bike over two years ago & the paint is holding up really well. While paint will never be as durable as powder, for a street bike it's a good way to go. We pulled apart a '00 FXDS (Low Rider) & had all the motor cases & lower legs powder coated for a customer. The powder bill was over $600. We spent less than $100 doing the Sporster. You can set them side by side & can't see any difference in the paint/powder.
You're gona' have to take the bike apart to do this right! But, if you'll take your time & do the prep work, you'll be real happy with the results & save yourself a bus-load of money.
If you need any more info, or if I can be of ant help w/this, E-mail me @: firstname.lastname@example.org
Have fun with it! It will completely change the look & attitude of your R/S. JW