Yes, it can be removed, but it's a tricky operation and can be bunged up easily enough.

If you remove the petcock sediment bowl and look up in there, there should be a little circular screen fitted up in there.  Remove that screen part, and you'll see a single phillips screw up in there that holds the petcock on.  The petcock-to-tank is sealed with an oval-shaped O-ring.

Those phillips-head screws are made from the same soft pot-metal that the engine case-cover screws seem to be made of, and can strip the phillips head super easy.  Get a good-fitting impact driver and get it out.  Clean / refurbish as you see fit.  Many times you can find a whole new replacement petcock on ebay. 

Good luck!

Kirk