If it is specific engine paint, I beleive it is designed to be used without primer. I'd read the paint can, it should say.
I've never primed engine parts before painting them
Motorcycles are not a form of expression, if you want to express yourself, write a poem, if you want to ride, get a motorcycle.
1986 Honda Shadow VT1100 (sold)
1957 BSA Bantam D3 Major restoration project
1981 Honda CB750F
2008 Kawasaki KLR650
2011 Triumph Sprint GT
2006 Kawasaki ZX14 (stolen)
2006 Yamaha FZ6 (sold)
1999 Honda Shadow Aero 1100 (sold)
1980 Yamaha XT500 (sold)