Front Sprocket Leaking Oil

I have a 2007 kx250f that has been leaking oil out of the front sprocket. It was a small leak and I replaced the two o rings in there even though they looked fine. After that the leaked slowed but didn't stop. Since it kept leaking I put a 3rd o ring in there just to see if it would help but no luck. After my last race the bike suddnely started leaking at a much increased rate. I am hoping there is nothing major but a friend of mine said it might be one of the bearing in there and that had happeened to him on his Kawi street bike. I have 3 more race weekds this year and I am wondering if its safe to ride as long as I make sure it has enough oil before each race. Also, does anyone have any idea what the cause might be if its not the o rings?



Don't race with it.  Just replace the countershaft oil seal and you should be fine.  Seal can be pulled and replaced without any motor disassembly.  Buy two seals, they are cheap.  One for backup.  Common cause for this is pressure washing around the sprocket.  Clean everything good before you put the new seal in.

Thanks, how do you get to the seal? I was looking at the diagrams and couldn't figure it out but I'm not in front of my bike to compare. If I pull the sprocket there is the spacer and the two o rings. Is the seal right behind that? Can that be pulled just by removing the sprocket as well? Thanks.

The seal is what the spacer slides into.  You will find it under crankcase in the OEM fiche at Rocky Mountain.  Part number is 92049-0030.  Yes, just remove the sprocket.  You can pull the old seal with a pick, screwdriver, seal puller, or other methods you can research on this site.  Don't damage the case.  Just clean up good and put the new one in straight and drive it flush with the case (as yours is now) using a suitable seal driver.  Helps if the seal is cold and the motor is warm, and make sure you oil up the mating surfaces.  

Thanks Again.

No problem. Check back when you get the seal and let us know if you have issues removing the old one. Should be pretty easy, but get two, just in case. Then you'll have a backup.

easy way to remove the old one is to use a wood screw and screw directly in into the seal after removing the collar.

then just use pliers and pop it out. Clean the case well, apply a bit of sealer on the new seal and carefully tap the new one in, you can use a wood dowel to do this on the outer edge of the seal casing. make sure you only drive the seal till its flush. It will be able to go all the way in as it has no raised lip.

Also there are two o rings that go on the inside of the collar / on the shaft. make sure you put only two or it will damage one of the seals and leak.

Had a big problem with one bike where it had chain wrap damage there, took me a while to make it seal up with out changing the engine case.


Changed out the oil seal and everything is workign perfectly. No more leak for the first time in a while. Thanks everyone for the help.

Sweet!!! Always good to hear when things work out. Ride safe and have fun!

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