I've been having problems with my gun. I can spray the basecoat just fine, it goes on smooth but when I spray the clear coat it orange peels like crazy!! I adjust the nozzle between stages so I am thinking maybe the nozzle is too big.

Its a 1.5mm nozzle. I'm using a urethane-based Western "Dimension" clear "overall clear" that uses a 4-1 ratio of hardener, no reducer.

Would it be possible to add reducer to the clear to thin it up some? The spec sheet on the clear doesn't say anything about it so I'm not sure if it would cause a reaction or not.

And is a particular size tip nominal for urethane-based 2 stage paints like the kind i'm using? I can get a 1.3 or 1.4 if needed.

What is the make and model of your gun? What air pressure are you spraying at? Bob

ignersoll-rand 270g 40psi

you'll get the best results with a 1.2 or a 1.3mm tip, it atomizes the clear better... shoot with 100 psi on the wall, and like 25-30 psi at the regulator on the gun... also depends on your technique too, if you go too fast then the clear will orange peel, but if you go too slow then it will run, there's a fine line... it takes some getting used to...

I've never been able to spray clear smooth enough without adding reducer.
I know a lot of people do but I haven't been able to.
Different clears are different viscosities, I've had some like water and others
are so thick there's no way you wouldn't thin a little.
I've tried all different tip sizes and have gone back to what works for me,
adding reducer and using a little slower reducer than what's recommended.
Just be sure to allow longer time between coats for flashing when doing this.
I have one reducer that's so slow it takes 45 min to flash, but it lays
the clear on like oil, I use it for bumpers that I don't want to buff out.
I've talked to ten different painters and got ten different answers.
There's good advice on this forum but everyone "tweaks" their settings a little.
You have to find what works best for you.

Sounds like your not putting it on wet enough or using to fast of a hardener for your shop temperature. A smaller head will atomize better but you can usually compensate with higher air pressure.