I had The same problem on my 2011 300 six days. Apperently GG changed carbs this year from the Air Striker 1 to the 2 model, and used the same jetting as the 1. I had to drop a my pilot from 42 to 38 and main from 175 to 170, lower the needle to clip one. It still wouldn't idle and plug went lean at 1/4 throttle. the ticket that made my bike awesome was change the needle from a N1ef to a n3eh in position 3 ( middle clip). I ride at 2000 to 3500 ft regularly,and 55 to 75 degrees. so far so good. the plug is now carmel color and power is awesome from bottom to top. I also went from stock hitting reserve at 35 miles to now over 55 miles. I don't know what needle the 250 has but I would guess it might have the same one. I got the needle from KTM. Don't remember the part #. The needle that came in the bike had the wrong taper was the main problem in my opinion. I will drop the needle one clip and main to 168 when it gets hot here in AZ.
