replacing crank seals?

[1998RM250]

Well after trying to get my jetting right on the 01' RM 250
it seems to be running better (no more bogging) but still doesn't seem to have the power it should... I've got about 8 hours on the rings, and It hasn't "appeared" to be burning any tranny oil. The bike is still spooging alot though even with new silencer packing running yamalube 2R @ 32:1, after one 5 minute blast around the trails you can already see it accumulating on the rear fender a bit. I thought if it was burning case oil you would at least smell it, and it doesn't smoke a whole lot either which is weird. If worst comes to worst and I have to replace the crank seals do the cases HAVE to be split? I could have swore I heard someone replacing the wet side seal without having to split the case, but I may be dreaming? What about any oil additives, are there any that might help expand the seal or is that a bad idea? I've been running 10w30 mobile one, but I think the previous owner was running a thicker gear oil. Would switching oils cause the seal to go bad faster? I just want this bike to run right, i hate riding it knowing there is most likely an underlying problem... I also noticed some smoke coming out the pcv valve hose the other day, but then I seen a brand new gas gas 250 doing the same thing so I figured it was normal? Thanks for all the help guys... :bang:

 

[KX_OUTLAW]

Do a crankcase pressure test.

 

[eagles22793]

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

 

[1998RM250]

I was just afraid i wouldn't do that test right and really end up blowin out a seal or something... Now that I think about it, the bike ran right for awhile when I first got it so I'm wondering if changing from a gear lube type oil to the mobil 1 had something to do with it? I had to raise the needle jet clip up two positions (2nd from top) just for it to not bog anymore, but yet the plugs still look like burned on oil or something!

 

[lmidden]

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

 

[whenfoxforks-ruled]

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

 

[1998RM250]

Wow thanks the bike is actually is an 01, and when I took it apart had no play in the crank supprizingly. Started off with a new sparkplug today (br8es) and by the time i ran a tank though it, it just died out of nowhere. Pulled the plug on site and it was wet and oily with fuel. I've probably put about 10-12 hours on these new rings and I didnt think they would be shot that quick, but i do ride it pretty hard. I guess it's time to pull the top again and replace the piston this time too? I've been running synthetic mobil one, should i switch back to a conventional oil? Thanks for all the advice, its greatly appreciated. Today was rough out, ate it a few times in the sugar sand berms but only because I was riding really hard (or at least trying)! Also I can get a good deal on a complete 1999 top end kit, would it fit my 2001? Part # 12101-37870
I cant seem to find any info!