Originally Posted by
ultraman6970
Nah the hardener is not necesary u can just paint using the thinner, just have to leave the frame drying for 3 days before start touching it and sanding the imperfections. At least under my experience u can leave the hardener out, but thinner is mandatory or you will clog the gun right away
Depends upon the paint composition. Two-part epoxy paints or polyurethanes will remain gooey and runny forever without the activator. Adding just the reducer makes it thinner and easier to spray on a smooth layer, but it will never cure and harden. Of the two parts, only the reducer is optional. Lacquers only need thinner, but those aren't good paints for bikes or parts that experience flexing.
I've sprayed Glasuri, DuPont, PPG on cars, motorcycle and bikes for the past 30-years. Look up the manufacturer's specs on what each paint needs. Each composition is different.