Jonathan,
For primers, I use DuPont Corlar (epoxy) or Por15 (urethane.) If I expect to lay it on heavy and cut back, I use the epoxy, as I know it will cure in 24 hours regardless of thickness of application. If I do not expect to much of any sanding, I will use the Por15, which gives a very hard and durable surface. Too hard to readily sand, as it quickly blunts silicon carbide paper! This can be an advantage, as if there is minor pitting you can primer with a light coat of Por15 and then go over it with a rapid fill primer made for sanding back. It is then easy to sand back to the Por15, at which point the sandpaper stops and you need not fear so much cutting through the primer. The a second coat of Por15 to cap it off. If I expect to do a lot of sanding, cutting back the primer too, then I will use the Corlar. It does not sand very well, but it can be sanded.
The rapid spray fillers are usually a polyester.
For top coats, I have been using standard automotive acrylic enamel. Generally DuPont Centari, mainly because it is readily available more so than I think it is the best around. To this I usually add some of the optional gloss hardener component. This tends to counteract a tendency of Centari to orange peel, and as the name suggest accelerates the cure and makes it possible to compound the surface as traditionally done with lacquer. This is particularly handy with larger surfaces where orange peel would be more offensive. Beware, too much of the gloss hardener alters the surface tension of the paint, causing it to pull back from sharp edges, reveling the primer below. On petrol tanks I will also add a clear coat of the same acrylic enamel after lining and transfers. I usually give it a dry dusting over the transfers and let that dry before giving it the proper wet coat, and so far have not had problems with the paint attacking varnish or water slide transfers.
I did one frame early one in lacquer primer; never again! It is too brittle. Between bolting the bike together and stone chips, you will be hard pressed to keep the top coat intact. I also did one frame with DuPont Imron (Polyurethane) top coat as I was lead to believe it was tougher than the standard acrylic enamel. It was not, it is just as prone to stone chipping as anything else. It just cost even more and is more trouble to spray. What it is excellent for are large surfaces left out in the weather. A friend had a small airplane painted in Imron, and while it chalked out in the sun just like a acrylic enamel, it took far, far less time to buff it back into a high gloss. However you will probably not be leaving you cherished motorcycle out in the weather, so I do not see any advantage to using Polyurethane as a top coat.
By the way, besides the general health hazards of spraying paint and volatile organics floating about, any of the two-part paints and the hardener/accelerators for the acrylic enamel are carcinogenic. So carbon filter pack respirators or better yet a positive pressure fresh air supply to the mask is to be preferred.
Powder coating is o.k. for small items like wheel stands, but is generally too thick and soft for the frame. It will extrude out from any fastener/component clamped onto it.
Regards,
-Doug
