I wonder if POR 15 might work. I have used their PC Glisten clear on forks and it has held up nicely, very tough coating indeed. Stumbled apon it whilst looking for coatings for my rusted trawler.. They have different colours including a strange green which i used to paint the 2 stoke diesel ( 471 GM) in my trawler. yes its also 2 stoke, but does'nt have an expansion chamber, just a nice blower..., i will look up their website for the colours as i migth want to paint my ktm sliders.