Make sure that the vents on the gun are clean and if the problem is still present then you have a problem with wear on the bushing or the needles. Air is blowing back into the cup before the needle is opening enough. So this could be a pressure, timing or wear issue.
SOURCE: vaper primer gun has intermittent air supply
Does it come with instructions? The material thickness is VERY IMPORTANT when choozing the proper nozzle.
SOURCE: Gravity feed gun has bubbles in the cup
I was in desperate need of getting on with lacquering a guitar and it seemed everywhere I looked on the net just gave actual spray pattern issues.
There was a small article that suggested tightening the nozzle up. I had only finger-tightened it.
Problem now solved!!!
SOURCE: Hello, the gun has been
as you did not provided exact model - i assume that this one is gravity feed.
this is generic solution for your problem, assuming that there is no crack in the nozzle.
you mentioned that you cleaned it - did you removed little filter on the bottom of the cup and changed for new? they cost just few cents each and get clogged easily. replacing them is more cost effective than cleaning them.
now, i would suggest removing paint from the cup, wash with appropriate solvent and spray little solvent through. fill now cup with about 1/3 to 1/4 paint stripper and spray that to sink or other receptacle - DO NOT FORGET GOGGLES OR EVEN BETTER - FACE MASK! YOU HAVE ONLY TWO EYES AND NO SPARES!
just in case - prepare 2 or 3 pints (1 to 1.5 liter) of water with few spoon of vinegar in it - it will neutralise paint stripper if splatter on your body or paint which you want to preserve...
now, prepare sheet of butcher paper, pull gun apart removing the needle, check tip for dirt, damage, bends - clean and repair if necessary or exchange needle for new one. needles are usually made of stainless and have dull sheen on them
check nozzle - remove any residual paint, check for cracks and any physical damage, i do that usually at 20x magnification for airbrushes and 5x for other air guns. there are temporary repairs to cracks but usually replacement is only solution.
grease lightly all springs and working surfaces with ptfe dry spray, if you do not have that grease, use petroleum jelly (vaseline).
put gun together in reverse order in which you disassembled it (you put parts in the order on the butcher paper? :-)).
now, i assume you know what each button do on your gun, but just in case, bottom screw (closest to the air input) regulates airflow to the gun, middle screw regulates volume of the paint, and top screw or in some models side screw regulate pattern. close all screws.
fill cup with water (you did insert new filter?), there should be no leaks of air or liquid anywhere, needle should be not retracting.
open air volume screw on the bottom to the desired pressure, in case of water based paints - it is about 40 to 60, depending on the thickness of the paint.
hold needle retracted and lose the liquid flow till you achieve regular flow from the nozzle, on vertical surface for about 15" (400mm), diameter of the water circle should be about 8" to 10" (200mm to 250mm), it can be bit more if you are using very, very thin paints, inks for example or solutions,
now, go to third valve and open it till you acquire desired oval.
that is all what it is for setting up any airgun, including airbrush (only diameters and distances are smaller).
now, water based paints have nasty habits of precipitate from the solution, only way to avoid that is to shake it well before every refill of the cup and filter as it go to the cup. 100 filters will set you about $15.00 in paint store (in hardware store it will be about 10 of them for same money....).
now, we check everything, is clean and spanky - and still clog the nozzle... problem is paint is too thick and you need to replace nozzle for large one, most "solid" water paints require at least 1.8mm nozzle and up to 25% dilution, i am usually using 2mm or even 2.5mm or bigger nozzle for water paints.
if you try to spray water based latex paint - you need a minimum 2.5mm nozzle, i am using even 4mm for that particular paint.
if you find my answer useful - do not hesitate to put some points my way... if you have any questions, including some clarification - feel free to ask.
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