If it is high build primer, that could be part of the issue. Hard to say, though. I usually use a very old copy of a very old Binks siphon design which I've increased from 1.8 to a shade over 2mm...maybe 2.1mm. I didn't expect the increase to make a big difference but it did. Also with that larger tip I lowered the pressure a wee bit (a shade over 25 psi) and that helped with the thick stuff...but as I mentioned earlier I have to watch how I spray now. At times in the summer I just use plain old lacquer type primer and hot temp reducer. Like this:
https://5staradvantage.com/product/301/ I know...folks don't like it these days but it works in hot weather as long as I cut it 1.25 reducer to 1 primer. The red was my choice but it is discontinued.
A friend went to Harbor Fright and bought 4 of the HVLP guns they occasionally mark down to $9.99 each. He increased one to 2.5mm and the other to 2mm one to 1.8mm and one to 1.6mm (I believe they are made with a 1.4mm tip) and says they spray about as well as anything he has if he cleans them really well after using.
