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Discussion Starter #1
I am trying to figure out what I did wrong in adjusting my cheap spray gun before spraying some Epoxy Primer on my '69.
I cleaned the new gun with laquor thinner real well first, then used water in the gun to do some test patterns while adjusting it out. It had a good slightly oval 6" pattern.
I mixed up some Epoxy Primer 4:1:1.5 and started shooting. It did not cover well at all. In fact, it looked like it had no pattern what so ever. I adjusted it some more and got about a 1" pattern and that's about the best I was able to do.
Any ideas on what I did wrong and how to not do that again?
 

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No expert here, but my first guess would be wrong tip size, or inadequate pressure......Jan/SeanD/or Steve-O would have to confirm/refute that, though.
 

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It sounds like what mo2872 said, to small tip for that type primer, you didn't mention if it was high build or regular primer.
If you don't have a larger tip, thin it down and up your pressure to 45lbs and use more coats , unless you are using a HVLP. then that would be too much pressure. "You can only expect your game to be as good as your equipment".
 

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Discussion Starter #4
well, it is a HVLP gun with a 1.8 tip. Regular Epoxy Primer (Matrix brand). I started with about 40 lbs of pressure through the regulator at the gun. by the time I was able to get it to work somewhat, I was running about 110 lbs of pressure through the gun. Evan a POS like the one I have should not be working that bad. I am beginning to wonder if the primer was not reduced enough, but the guy at the paint store who uses this stuff all the time said I should not have to reduce it more than about 4:1:2. I don't know, I am certainly learning here and considering popping for a low line Iwata with a 1.8 tip to shoot the trunk area after I get it cleaned up and to spray the high build primer when I am ready so I can block sand it smooth.

I have a low line Iwata with a 1.3 tip for my base coat and clear coat. (I haven't played with that one yet, but I will certainly do some test panels before i get to painting for real)
 

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That does sound odd, Daryl. I will defer to the pro's, because my only solution would be play with the knobs until it works better.....but 110 psi.....sounds like it was too thick a mixture, to me. From what I've used(House of Kolor), it's only been a 2:1 mix, so that may be the rub, there.
 

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With a 4-1-2 mix and 1.8 tip, you should be good to go with a HVLP with no more than 10 psi at the TIP, even with high build!
 

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With 4:1:2 mixing and a 1.8 tip and needle it should flow pretty well, i see you tried to set the pattern first with using water, that is a waste of time, same with trying to set it with thinner, as those are thinner than the primer it gets a totally different setting.
Also using lacquer thinner to clean the gun isn´t very good, to clean it you should use a cleaning thinner such as a Cellulose thinner.
Now for the low flow problem, is the vent hole in the cap open ? if that is clogged, then you get a small spray pattern and trouble getting the primer from the gun to the car
 

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Discussion Starter #8
I thought the vent hole was open, but it could have been clogged when I tilted the gun to spray a flat panel..... ( the cup was pretty full with only about an inch of room from the top)
I will clean the gun out thouroughly and ensure everything is open and try some test panels again in a week or so to see if that might fix anything.
Thanks to all who have responded, it has helped for sure.

Things I have learned from this:
1. Don't use water to do a test pattern as it is too thin.
2. Make tripple sure all the ports are open and clean (which I thought I did)
3. 4:1:2 with a 1.8 tip should be thin enough to spray well.
4. 120 psi at the gun should not be required to spray, it should be about 40 psi at the most.
5. mix a very small amount of primer to use for test patterns so I am not committed to spraying a full cup with a Messed up gun/pattern.
6. Use a cellulose thinner to clean the gun and not a laquer thinner.
 

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Good luck Daryl! You are picking up on the fine art of how easy it ain't! LOL --- about 30 PSI is what you want at the tip with the trigger pulled. Depending on how much flow your compressor can handle you may want to work slow so it can keep up as well.
 

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You learn well Grass hopper. When you get around to the paint, remember, always use a primer or sealer close to the color you are painting, I recommend a sealer tinted to the paint color, that way you don't have to use as much paint to cover, especially on transparent paints.
 

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Daryl, one thing you haven't mentioned is the paint flow adjustment and where you set it. this is what controls how far the main needle (? lack of better term?) gets pulled back to allow the paint to flow into the atomizer section of the gun at the front. On ny HVLP, I set it to 3 turns out from fully closed. Let us know what that setting is. You already mentioned how you adjusted the air pressure, so you're up on that. As far as the paint mix ratios, I'll have to trust your numbers (the epoxy primer I buy is simply 2 parts primer to 1 part catalyst). I use a 1.4mm tip with no problems.

Another thing that's not mentioned is your air supply- especially with 120 psi that you tried (yikes!) I'd expect your compressor to be running full blast- do you have good water separator installed at a point just before your gun (air needs to be cool for the water separator to work).

I've had primer rust quickly on me before I got my compressor and lines up to par, and my theory is that water was getting into the paint via the compressed air from my struggling compressor and improperly treated (cooled and dried) compressed air. Let us know and good luck- nothing beats being able to use a paint gun!

Kevin
 

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Discussion Starter #12 (Edited)
Kevin,

I am using a single stage compressor with a 60 gal tank that will put out 10 SCFM @90 psi. I have a bout a 50' run of line to the back of my garage with a decent water/trash filter in place. I ran about 30' of hose from that to the gun with a little filter dryer at the gun just after the pressure regulator.

I had adjusted the paint flow needle screw by: unscrewing it all the way out untill it just hung on by a thread then with the trigger pulled, screwing it slowly back in untill it started to move the trigger. I locked it down there. I read somewhere that was the way to adjust it. But with the results I got, I am not taking anything for granted at this point.

Again, thanks for the guidance.
 
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