As HRL has pointed out, pretty much any oil based or silicone based contamination will result in pin holes/fish eyes. Also, possibly it is too heavy of a coat. As long as you're shooting a sanding primer, try reducing the thickness of the coat while spraying.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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