Mikuni Piston Slide no "CLUNK!"

Hey guys so I'm having some issues with two of my mikuni carb pistons. Two work as they should, you can hear a nice suction sound with a solid clunk when it seats. Now to eliminate some things all springs are new and in great condition with no kinks in the spring. The boots seem solid. I couldn't see any tears and held it up to the light to see if there were thinning areas which there are none. I've taken out the the needles to see if there was any rubbing and neither of the two non working pistons are effected by the needles. I am going to post a video to show you guys exactly what I'm talking about as soon as the video is uploaded. Now the pistons with the needle assembled will easily drop into place without the spring and carb hat on, BUT when I seat the boot and put in the spring and put the hat back on the piston will no drop with a "clunk" it seems a little slow but nothing awful. I've read other threads dealing with this issue but none really explained the problem I am having. Please let me know what you guys think!!! Thanks!

 

this might help
http://www.xjbikes.com/forums/threads/please-define-clunk-test.44738/
See what bigfitz says

 

The one on the right is falling too slowly. Have you checked all of the air passages for blockage (not just the air jets)? Don't forget to check the vent that connects the top-hat area to the kidney-shaped orifice on the front of the carb.

 

If you don't find an issue with the vent as K-moe suggested try swapping the spring/diaphragm/piston assembly between the two carbs and see if the problem follows.

To me, the one on the left looks too fast, and the one on the right looks too slow.

Not sure on the Mikuni, but on the Hitachi there are two holes in the bottom of the piston that when correctly oriented face the front of the carbs - make sure they are clear and the same size on each slide. I am thinking those holes are sometimes modified by PO's trying to fit pods.

 

I will give your suggestions a shot fellas. As for for the little kidney shaped vent hole k-moe was talking about it is completely clear with no restrictions. It's odd that yesterday when I tried the clunk test it didn't clunk and when I tried it again today the non working pistons clunked!! but not a very solid sound like the ones that work as they should...perplexing...