On a dirty, greasy, oily item like a motor you should consider using TSP before painting. Tri Sodium Phosphate - a severe duty degreaser and will etch anything you use it on - simply hose off after washing. Big box store in the paint prep section (TSP Substitute by DAP)
As for a good primer I would suggest one from the same mfg'r of the paint you are going to use.
Thanks. I will pick some up. I have used engine degreaser already and it's pretty clean. I am using color brite OEM factory Yamaha bluish gray paint and their clear coat but can't get the primer locally. I was thinking of using mar pro zinc chromate primer but wanted to see what else is an option.
I should be shooting the primer by next weekend after some final prep work.