I rebuilt the carb over this past winter. Tore it down, baked it clean and used a rebuild kit. I believe the carb is in good shape. I did change the jets based on recomendations from the Suzuki service manual and also FMF Exhaust's web site. I cleaned the reeds but did not replace them.
How did the reeds look? Obviously you would have noticed any chips but did you check to make sure they were sealing well?
Did you check the float height during the rebuild?
How many turns out is your air screw and how did you come to that setting? Did you follow a procedure like that mentioned in the second link I posted? That's a good place to start to determine if you have the correct pilot jet size.
I rode a '98 KX250 last season for woods use and if you ride like I did with a 250 MXer, you probably spend the majority of your time below half throttle...or maybe you don't. Who knows?
Getting the pj sized right and needle position set is crucial for good low-mid performance, especially if that's where you spend most of your time riding. I believe my KX was used for ice racing and was jetted richer(several sizes up from stock) when I picked it up. Fouled plugs occasionally early on so I went back to the stock jet sizes and tuned from there. Spent part of a day at FVOR screwing with it tuning the AS and eventually dropped the needle one clip from stock. I probably could have dropped another size on the pilot. It still was by no means perfect but it was no longer fouling plugs. It started up easily, idled smooth, had crisper throttle response and felt strong through the entire rev range. Still on the rich side but was good enough for me.
My white tail plastic is always oily after a ride. Does this indicate too much spooge or running too rich or perfectly normal for a 2-smoke? I run full synthetic at around 50:1 for what it's worth.
Everyone has their own opinions on what ratio to run. Have you always ran 50:1 or did you change from some other ratio along the way? Whatever you decide to run ratio wise, stick to it. Don't change it to solve jetting issues.
My KX still spooged. Occasionally enough to produce a light spray on the rear fender. Didn't make a difference with fresh packing either. As long as the bike ran well to my expectations, it didn't bother me. The KTM 150 on the other hand produces very little. Just enough to coat a small area around the very tip of the silencer. No spray anywhere. Two different animals though that get ridden very differently so that could have an effect.