I have a '99 WR400 and it has a very slow oil leak from the primary drive shaft seal. It leaks from between the seal and the drive shaft. It's not alot, but enough to leave an oil mess around the case area after each ride and several drops of oil on the garage floor each night. Anyway, I am mechanically inclined, but have never split cases and I am assuming I need to split the cases in order to push this oil seal out from the other side of the case? Has anyone done this before, or at least split the cases? Is it a big job, or not too big a deal? Should I leave this one up to the dealer, or give it a shot? I would especially love to hear from anyone who also had to change this oil seal on the primary drive shaft (front sprocket).