Hanging idle?
 

Does this sound like hanging idle?
http://www.youtube.com/watch?v=ZEbkhuL26HU

Not really.. if it is a little tweak of the air screw or dropping the slide a bee's dick will see it gone.

Usually a hanging idle/racing/surging will present more so when the engine is at full temp and has had a load on it.. Think of what happens as you run out of fuel and she starts to nang and race up before it dies.

Like this.. https://www.youtube.com/watch?v=FM4EUKrrymM

Ha, I had that recently with a crushed fuel line.

On my last ride, I started experiencing a surging of idle, one point the bike wouldn't start without the choke. At first, I suspected that I may have soaked the air filter as its wet as hell around here, but much to my delight the airbox on this 18 is very tight(my 13 air box always got soaked). I suspect that the pilot jet may be plugged, just have not had time to pull the carb and check. I think Jakobi mentioned he found so plastic in the tank, I remember finding the same in my 13.

I have exactly the same thing with my 300 2018!
NEDW at 2 172/42 AS 1t

There are still 2 filters in the tank which should well and truly take care of any material left over from manufacture. I also like to install a further inline filter between the carb and tank for piece of mind.

If you can confirm good fuel flow from the tank to the carb, then have a look at the carb. Wouldn't really expect blocked jets but anything is possible.

Air leaks can cause similar symptoms leaning everything out too (stator seal, cases, reed block, etc). Again, would not expect to see anything on a fresh engine, but sometimes things happen.

If all that is well, then you could simply be a touch on the lean side. I haven't jetted one of these engines up yet so everything I've previously said about W and J diameters is in relation to the older engines 10-17 models. Changes have been made which can influence things.

The other consideration is the engine. TSP (Australian 2T tuner/performance shop) has noted a large variation in engine tolerances. His words, "got 4 heads in from a dealer from 4 untouched bikes (2 GPs and 2 ECs) and got 4 different squish measurements... 1.3, 1.6, 1.8 and 2.1. Heads of the same part number are measuring up different as well."

If you consider that those heads would all be running very close volumes that gives a wide range of compression ratios, which will definitely impact on how much fuel a bike needs, and how it feels off idle.

The other point to note is that what we are finding nice in Australia is always a bit different in other parts of the world. A cold day for me is 15C and it's almost rare for temps to drop below 10C. My average temps are usually mid to high 20's going up into the 30's in summer; and always with a healthy dose of humidity on top.

I really hate in line filters. Oh I use them where I can, but often the are the the reason a fuel line needs to kink just enough to be trouble. I bought a right angled one but was still a bit clumsy. We need curved ones.

Well got a chance to pull the bike apart and take a look. Carb was clean, plug looked good. However, I did notice one of the overflow lines on the side of the carb was kinked, trimmed it down. Pulled the petcock assembly and found that the filter at the top of the tube had come off, doesn't seem like it will stay so I will go with an in-line filter.
Haven't had a chance to fire it back up but will get to that tomorrow. The bike ran great but later in the day the surge started while riding it wasn't bad just when I would let it idle.

Well, I looked at it today, while idling down to a minimum, no more hanging problem! but it sometimes stalls the idle is too low!
the air screw is perfect at 1.5 turns.
I will try to put a jet of 45 and open more screw air, it will bring down the slide for the same regime and avoid this problem.
otherwise, she is perfect with NEDW.