I am far from an expert - am only passing on what I learned from Strick here on DRN and James Dean over on the Holeshot KTM jetting forum -
I had same problems, right off idle and low speed riding bike would load up and foul plugs- the #7 slide and straight taper needles as suggested absolutely corrected it - now my plug reads about perfect no matter how i am riding be it WFO, just off idle or in between. As my bike is a 300 my specific jetting wont likely apply nor would my specific needle - but it is the way to go in my book. Messing with Pilot jet, main jet and clip position never really touched the real problem area. (did end up going back up a couple jets after the slide and needle though)
In addition to the specs James Dean supplied be sure you have replaced the stock exhaust (both pipe and spark arrestor) as the stinger section is too small, I used a FMF Gnarly and Turbine Core setup I got from MXTuner. Also the reeed spacer which is an aluminum plate you can get from your dealer will help a bunch. Some folks swear by the compression release hole drilled in the cylinder as a way to end stalling problems. Also some early '96 bikes had a casting number of "1" on the head and later bikes had a lower compression head with a "5".
I doubt you'll get the bike to run completly right without the exhaust. It was a serious design flaw that cripples a really awesome bike.
The compression hole is a hole drilled in the barrel. I do not recall the exact specification right now but this is not a do it yourself with a hand drill type of modification. There are several shops that can do the modification for you but to be honest save the money and get the exhaust first.:)
I had similar problems as you with my 96 360 E. As Patman stated, the earlier cylinders were stamped with a 1. These cylinders were of the higher compression and are difficult to jet. James dean has provided the cheapest way to correct the jetting problems. I also did the Rad valve, FMF exhaust, and reed spacer thing on my 360. I was able to get it to idle and not foul plugs with a very similar jetting set up as James Deans describes. If you are using the stock exhaust, when was the last time the packing was replaced? If it is running as rich as you desribed and it's 4 yrs old, the packing may be saturated with spooge. That will impact performance as well. When you get this thing right and get a clean running bike, you will be smiling from ear to ear. Gobs and gobs of low end billy goat torque that will rev to the moon. You wont be asking, "how fast is this thing" but more on the lines of " I hope I have enough room to stop this thing!!" I'm smiling right now thinking about those fire road drag races!! Good luck.
99 300 EXC
96 360 EXC Memories
I don't remember what needle for sure and I sold the bike. DON'T use non-resistor plugs you WILL toast the ignition module!!! The bike will never run close to right if your keeping it choked with the stock exhaust and don't have the reed spacer in place. You MIGHT be OK with the spacer & #7 slide but it will still not run clean. I sold mine for $3K with a fresh piston & rings, Eric Gorr porting and power valve setup, full MX-Tech suspension, FMF exhaust, and it was in perfect condition.