Around 3600 or a bit faster is where you transition from the pilots to the main jets when the engine is under load. So, run it a bit on the road holding the engine speed around 2500 and check the plugs. I'm thinking that is where you are running extra lean. If so, a little bigger pilot jets and maybe Thunderbird Spot needles with a shim or two should help.
Unless you are able to hold a fairly constant speed for a couple hundred miles, you won't build up any significant deposits on the plugs, and slowing the bike with the engine running can give you a false reading. That's why you will constantly be told to disengage the clutch and kill the engine first, then stop. Even then, your best place to look is deep inside the plug where the ceramic is in contact with the metal base. That's where the ceramic runs coolest and deposits will condense more.
