Cylinder 3 misfire at low revs

[His Dudeness]

Brilliant  :thumbup
I knew that it was essential that the diaphragm should be in perfect condition and that  even a pinhole in it would render it useless, but did not understand how it all worked together.
Thanks again Dude for a very helpful post. 
  :woot

yeah if there's a hole in the diaphragm the pressure on both sides of the diaphragm becomes the same so the diaphragm won't deflect up properly so the jet needle won't lift up and the fuel mixture won't flow through the main jet