The only time I get smoke is on engine start.  I looked at the 2D, and noticed a 'smoke" switch, but it did not appear operational in the "Gmaxflight" model (the one with the blue and grey paint job).  Try toggling that switch in the ones you are having problems with (it's way down at the bottem, lower right, on the 2D panel  You can't even read it's purpose until you mouse over it).

I did notice that on the military models, if you start with engines on, and have the throttle full on, it belches black and grey smoke and the roters never spin up until you back the throttle down.

Have you tried pressing "I" for the smoke system?
Maybe the engines are on fire?
Does it do it for default planes and addon ones?

Hi Today I removed the file and replaced with the one from simviation and it's still the same, I've tried adjusting mixture,and removing and replacing files from effects in the hope one might be latching on, but no luck, I did notice that sometimes when I changed camera view from in to out it took about 2 seconds for the smoke to appear, Thanks again for your ideas, keep them coming,