Speckled paint job

Not sure exactly what you mean without seeing the picture.  You need to link to a photo host (like Flickr etc.) to post pics.  I think there is additional information on this in the "How To" area.

Honestly it could be a number of things. From how humid it was that day to PSI, to maybe a small piece of something was blocking up part of the needle, to what kind and how much thinner, what your angle to the surface was, etc. 

In my non-expert opinion, I usually get spitting like that when it seems I'm spraying with a flow issue in the airbrush or when I'm running too low a PSI with too thick a paint.

Yep, typically, spattering is usually caused by insufficiently thinned paint. Also, as mentioned above, your choice of thinning medium may also be a factor.

http://i1234.photobucket.com/albums/ff412/NeedBeer/DSC_0807.jpg

managed to sort out the photo - now on photobucket - see link here

The green was adequately thinned with Tamiy Accrylic thinner & I tried #1 and #3 needles both had same effect - compressor 15-20psi

have done two jobs with different paints since with #3 - one was fine & the other was also speckled/splattered

Wondering if its the compressor - sometimes when i run it on a big job the condensation gets in the paint but this is different because it spits out the paint

Maybe its to do with cleaning?

How much thinner did you use? I find that Tamiya likes to be thinned more - often more thinner than paint.

Also, the amount of overspray can vary depending on the distance from the subject and the angle of the airbrush relative to the surface being painted.

40/60 to 50/50 thinners/paint generally -normally get my best results with acryllic Tamiya so this result was dissapointing

- maybe I should try more thinners?

On the same job I did the oliver green without issue

last two jobs were enamels one was fine the other not

I am begining to suspect I havent been cleaning

If you can get the effect that you are looking for on occasion, I would say that it rules out your equipment & I don't think it's likely that your compressor is the cause. It would also suggest again that either thinning or the temperature & humidity of where you are working may have an impact on your results.

Adequate thinning is one thing, but for the type of job you are doing, even small differences in ratio can produce differing results. The addition of flow aid to your mix, like Liquitex Flow-Aid may help. A bit of messing around on some scrap plastic while adjusting the variables will likely let you figure out exactly what is giving you the variations in finish.

The general consensus on the type of painting you describe is to use as low an air pressure as your brush & paint combination will allow, but after recently doing a bit of playing around trying to get ultra fine, clean lines from my airbrush, I'm now confused;

Trying to get the thinnest line possible with Tamiya acrylics, using well thinned paint, very close to the subject with a fine needle, it all went reasonably well, I could get the fine line I wanted but there was noticeable overspray at the edges. To reduce the overspray I tried adjusting the thinning ratio, but this as expected gave poorer results either way & the only thing left to tweak was the air pressure.

I reduced the pressure as low as my airbrush would atomize the Tamiya acrylic at (8>10PSI) & tried again with little change in results, so I slowly increased the pressure to see if there was a pressure "sweet spot" which would give the least overspray. Up to about 25>30 psi, there wasn't really that much difference, but after 30psi the overspray started to reduce considerably.

The long & short is that I could get far less overspray working at maximum pressure (60psi) than I could at low pressure, this goes against what I understood about fine work, overspray & pressure. I'm figuring that either the paint around the edge of the airbrushes spray pattern was so dry that it simply didn't adhere, or that the increased pressure can hold the atomized paint within the airflow more efficiently for longer?

The picture helps a lot, as others have stated it seems to happen with thick paint or psi setting off, sounds like you adjusted for that.  I have a Paasche H also and leave the "1" needle in all the time but use enamels.  Given all the usual suspects for this problem, I will say that for some reason whenever I try to use white in the AB, I get speckling.  Now I have not tried another bottle (since I use it so infrequently) so it is possible, though not probable, that the paint is the issue.

At least that scapes the operator for the problem.