replacing crank seals?

Do a crankcase pressure test.

I think you will beable to get the crank seals out without spliting the cases I had a bike that would spit oil out also for a little bit then stop I think it was because I might of put a little to much oil in it so just ride it for a little while but keep checking the oil to makesure it stays full

when i replaced the crank seals on my yz it had to be taken apart but they might have changed the way the put the engines to get here since mine was built

Ring blow by will sure cause smoke out the pv hose, and spooge! A 98 of unknown history. Splitting the cases is not that big a deal. It is old enough for the rubber seals to take a crap, ALL of them. No up and down play at the crank ends, not even a little, none? The bore, it has even wear throughout the piston skirt and ring area? Has it been checked thoroughly with a bore gauge for out of round? How much skirt clearance and ring end gap? Looking at the micro fiche, I believe the no split seal change is very do-able, good luck with the ignition side though! I have never tried it, and hopefully never will. If I did, I would run 2 drywall screws into it, 180 degrees apart, and snatch it out with pliers, or block it and pry them out. Never pry directly against the case, a piece of wood is priceless. The right side can be grabbed from the inside, once the drive gear collar is removed. The collar, if you see marks where the seal rides, it is likely toast. Drag your finger nail across in both directions, if you feel it, it is toast, or get a magnifier and inspect it. They do make micrometers with a knife like edge and are accurate, but like dial calipers, they have to much variance and require a very good touch. There are a lot of parts in the engine, if you see wear, its bad or can lead to some problems quickly. The oil did it? There are some additives that can ruin the seals. Plain old regular oil, change it often, atf fluid, same story, a lot of automotive based synthetics and miracles in a bottle, NO! The factory made and recommended oils, are worry free, did I mention change it often, like a day of easy riding or 2~3 hours, at least. A leak down test can save a lot of head ache also. Vintage Bob