I thought that I should be on the lean side with this setup also. The pilot that I removed was originally a 52.5, but I was hoping to lean it out and fix the 30mpg issue. My fuel line is connected correctly.

The diaphragm is intact, I gently stretched it all around to make sure there were no small fissures. The slide was black and dirty when I first removed it, but I cleaned it up and had it looking shiny and new. It moves smoothly, with nearly no resistance.

I even took the carb off, drained it, and flipped it upside down to do the ol' blow in the fuel input hole and see if the needle is seating and forming a seal, and it does seal. When connecting the clear line to the bottom of the float bowl, it fills to about 1/16" below the float bowl seal, as I have seen in another post on here (thanks for this awesome resource and for sharing all of the collective knowledge!!)

But now, short of ordering new parts for all of the carb internals, I'm at a loss. All of the links and part numbers I have found on this site are all dead or out of stock. Any body have a good parts resource, with parts numbers as well?

I have only had the bike a couple of months. But it has gotten 30mpg the entire time I have owned it. It seemed to be running perfectly fine. Not popping, no sluggish throttle, it was a nice riding bike other than the crappy mileage. Then it started to get sluggish at idle for the last couple of days it was running, and I would have to give it 1/8 throttle at stops to keep the idle speed right. Then after a couple days of the slow idle, it died at a stop and wouldn't re-start. About an hour later I had gas everywhere, I guess a float was stuck. Cleaned the carb, and ever since it has been drowning. I'm guessing it was always drowning a little, but the dirty carb jets and such were helping reduce fuel, and now that it is clean there is too much fuel. But all the jets are correctly sized, the carb parts are Mikuni (although they have seen some miles for sure), and the float bowl fills to the correct height.
The end of the exhaust is black. It is definitely covered in a thick carbon deposit, indicating that the system is far too rich. My pipes also turned blue over the last couple of days on the bike before it crapped out. Also indicating an abundance of fuel. Why is there too much fuel? THIS I need to answer.  

Thank you for the link! My main jet does have a washer. I have ordered all new OEM parts. They should arrive in about a week, until then I will keep taking it apart and tinkering and trying it out over and over again. Hopefully something works.

Ok, so I'm still awaiting new carb parts, but I took it apart. Put a different needle and needle jet I had and the bike fired right up and ran perfect for about 15 minutes. Then it blacked out the spark plug again and it died. Clean the spark plug and it runs great for about 15 minutes, then dies again. It is idling correctly, revving responsively, and felt like a great ride. It definitely wasn't sounding or feeling like it was drowning. How could I be fouling spark plugs soo fast? Using NGK Dpr8ea-9 spark plug.

I will have all new Mikuni OEM parts delivered in 1 week, but I want to ride before then! All parts internal all Mikuni but are of unknown age and functionality, so I ordered all new ones. But this bike ran with the old parts, just got 30mpg. But it took over 500 miles to black out and foul the plug before, now it takes less than 5.

Care to walk me through that Gary?

Hey guys, update time. I tested the ignition coil, it got 3.9ohms and 11,000 ohms. I ordered a new one. Replaced the carb internals with all brand new OEM Mikuni parts. Replaced the ignition coil with one from EBAY ($13 score!) that tested at 4.1 ohms and 15,000 ohms. The bike now runs beautifully! I put about 250 miles on it this weekend, and now my mileage has gone from 30mpg up to about 47mpg! I think my bike is back to being happy. And after all of the parts that has gone into it, it should be happy for years to come. Thanks for all of the tips and advice!

I always like a happy ending.