I picked up a used BBK 80 mm throttle body. There is a thin layer of black stuff around the throat of the TB right were the blade sits at idle. My initial thought was a factory applied coating that helps the blade seal. Now I am wonder if this is normal or a build up from use?

 

its build up. go buy a can of carb cleaner and clean it up

 

I use carb cleaner or MEK.It will clean right up.
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2000 t/a ws6 with lots of mods

 

Thanks guys. Got it cleaned