Carb slide not going up not allowing full throttle RPM

It's pretty easy to misalign the little dimples (I'll call them) on the diaphragm when reassembling the carb.  If any air gets past the diaphragm, the piston is not going to go up when it should.  If you find you can lift the piston fairly easily and smoothly with your finger, I would not suspect "gunk" as the problem, especially if you just recently inspected them.

OK the results on the struggle. Always like to provide actual fix for problem for others to learn. After cleaning and reassembeling with everything lined up and perfect, same problem GRRRR. Tear it apart again and upon a more detailed inspection of the rubber diaphragm, there was a dimple/inconstancy in the rubber so moving my finger along the rubber showed some very small cracks in the rubber. Very hard to see.

What is the error chain that led to this? Customer pulled Carb and assembled and DID NOT line up the diaphragm tabs for proper alignment, first problem I found.

Second, he must have dimpled or put it on wrong folding (i am assuming) the rubber.

Third, I should have done a better job of inspecting the rubber diaphragm but it was only found by running my finger under pressure along the rubber diaphragm to see the super small tear. My bad not inspecting it better in the first place.....

Replaced the rubber diaphragm and it works fine.

Hopefully we all get smarter. Thanks all.