spray gun questions

[old_picker]

Just having a little problem with my spraygun
it was shooting lacquer perefectly till i changed the pressure at the compressor to do a hosedown of some dusty electronic chassis

now it is shooting in streams like um ssst ssst ssst ssst
the higher the pressure the closer together the ssst ssst's are in between the sssts their is no lacquer flowing [or water when i clean the gun]

i have the pressure high or low and change the pattern control and the airflow control here and there and i cant get it right - before i made the change the other day i could open and close the air control and pattern control however i liked..it seems to be entirely due to the pressure being changed and i cant get it back right - its stuffed

the pressure it was on originally i didnt write down

its just a simple S770 gun i bought from bunneys for $70.00 or so and 45 litre compressor

i have seen it before but got lucky one day and got it right - i shoulda never touched it

its not rocket science -
so what is causing it ??

[China]

Sounds to me like the holes in the air cap could be blocked, take it off and blow air through the holes

[Blackout]

Old_picker,

I can't offer any helpful advice but couldn't resist your comment that it wasn't rocket science when I work with 1/2 dozen Rocket Scientists who would argue that the domain jet control is part of rocket science. I must ask them to explain spray painting jets to me and see how confused I get when they start with the complex maths and physics constants. You should have seen me when they started explaining cyclones and giving me books to read.

When you fix your problem you should be able to say you know a thing or two about Rocket Science. Best of luck with the solution.

Cheers,

[old_picker]

actually i found that by tightening the nut behind the air needle valve fixed the problem

how it got loose i could not guess as it was fine before i changed the air pressure up....

no rocket science required as i found the answer in a similar post in this forum

[durwood]

Well done finding the problem so quick, there is not much to a spray gun so it usually can only be a few things wrong when it doesn't work.

What was happening was the air was being suckied into the paint stream and you were getting air and paint coming out of the nozzle.

There is a seal around the needle and the nut is to clamp it tight around it. snug it up as tight as you can without stopping the needle moving freely back and forth. The seal is usually leather (some of the cheap ones are plastic) so it should have a drop of oil (light macine type) on it to keep it soft. While you are there put some on all the other moving parts. Trigger pivot/air valve stem (also a seal) and the threads of the controls. When you have the gun apart also put a bit of greae on the needle and spring.

The one no/no is to immerse the gun in solvent, the only part that needs to be soaked in solvent is where the paint actually is which is the tube from the pot to the nozzle all the rest of the gun body only has air in it and you only wash away lubricant or introduce paint into that part of the gun.

[Harry72]

actually i found that by tightening the nut behind the air needle valve fixed the problem

how it got loose i could not guess as it was fine before i changed the air pressure up....

no rocket science required as i found the answer in a similar post in this forum

I was gunna say you got an air leak, I've found with cheaper guns that use cheaper metals that corrode... occasionally it pays to clean up any threads and mating surfaces with some W&D.