125-200cc Fouled Plug Question

Original owner of a 1999 WR125. It has not been raced but has not been babied. It was used for several years, sat for 8 years, and I started back up again last year. The bike has had almost no work performed on it and I actually replaced the original tire last week. There has never been a problem with fouling, but the past few times out, I have been fouling plugs. The plug is black and wet. I am using the prescribed plug, have not messed with the carb, 92 octane, 42-1 with Spectra. Just wondering if the piston/ring should be replaced after all of these years? I have no idea how many hours I have on it, probably 15 this year, and the same last year. Hmmm, at least 100 hours over its life, but that is just a guess. Would it be a good idea just to go ahead and redo the top end? Or mess with the carb?

Check the crank seal on the clutch side it may have began to leak from sitting so long, allowing oil from trans. to be drawn into bottom end.

That bike doesn't look to have that many hours Bruce, I'd guess under 20 from the pics you posted. Are you revving it or lugging it in low RPMs? I found my air screw turned all the way in recently as I was shaking my 99 wr125 down, and I ended up going to a one step leaner pilot too. Check your carb settings first, the air screw should give you good off idle throttle response from 1.5-2.5 turns out from full closed.

warm it up and do a compression test to rule out rings,go from there with the other things mentioned.
Did you drain the tank after all the years of sitting there? I have seen oil settle to the bottom of a tank and foul plugs after it had been sitting for a while.

The photo is older and does not include riding over the last 2 years, there are more scratches and dings, but it is clean relative to bikes this age. It has quite a few hours but they don't show. I did remove and clean the gas tank. I will adjust the air screw and not sure if I lug it any more than I have in the past. Response seems to be good. The crank seal is a good point. Thank you.

It this is a new thing happening, check the air screw just in case, but I'd be looking at the compression and rings/crank seal too. I thought it was in the same shape/hours as the flattering pics you recently posted!

It pretty much looks the same as in photo, I just notice every little scratch. The guy who works on it gets a kick out of its condition. He thinks it could be the jet or air screw. My guess is it needs rings. It is in the shop for new fork seals. I live here in hicksville USA or he is just inexpenisve. Last week, he swapped the tire for a new Michelin Starcross NHS that I provided, removed the rear wheel bearings to inspect/grease, and charged me $10... $8 for the tire and $2 for the bearings. Haha. It does not pay for me to do the work myself.

Would a compression test provide a definitive answer to the condition of the rings and whether that is the issue?