Briggs and Stratton 450E carbureter

As I re-call, the needle itself has a rubber tip, please confirm if so.
 
The only issue I had with that specific area of the needle and seat is the rubber tip
had a slight tear causing it to leak.  Check your tip closely for any damage.
 
A somewhat messy way to check for leakage is to hook up the carb to the tank with the bowl OFF.
gently hold the float up (closed) and check for any leakage of fuel. It should stay dry.
 
 
 
What exactly are your issues?   
 
 
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Apologies for last post , I lost 2 reply posts somehow. You were right about the needle valve, ( don't know why I thought there was a seating washer.) 
   I had leakage from the carb inlet overnight on a regular basis. Unfortunately, when I cleaned the carb bowl; the needle valve did not seat correctly, and I had a serious peak on my hands. Result was, 2 nice bald patches on the grass, and I actually acheived hydraulic lock when trying to start the engine.( Thought the pull cord had jammed )
 I will get a new needle valve and test as you suggested. Many thank!