By Jeremy at BlasterRiders
a coomon problem that usually leads to alot of time and misdiagnosis is a crank seal leak. the crankshaft seal on the right side (clutch cover) side is prone to leaking and/or being pushed out past its retainer. the most coomon symptoms of a leaking crank seal are: lean mixture, sudden excessive smoke from exhaust along with poor running, poor low end response( again with excessive smoke), and sometimes the dead giveaway is crankcase oil pushing out of the vent tube(near the headlight). what is happening is, when the piston is creating a vacuum in the lower end below the piston, it is also pulling transmission oil past the crank seal and burning it your intake charge. doesnt sound too destructive now does it? whats a little more oil? its not the oil you have to worry about just yet, its the huge vacuum leak past the seal thats of major concern, with the additional air passing by the seal, your running lean...VERY lean. also, if let go long enough without checking your case oil, you could end up running you case dry, but the poor performance would keep most riders at bay until the problem was solved.
now for the fix.
remove the clutch cover and clutch basket, youll now be able to look at the front main gear, if you see the seal pushed out, youll know it. this job is easiest with the use of impact wrenches to loosen the gear bolts. once you remnove the crank gear, remove the seal retainer and replace the seal. installing the seal is as easy as placing a light coat of oil on the seal and pressing it in with a socket. after that, install everything in reverse order and fill your case, change your plug and ride. you should notice everything back to normal.if you have any questions regarding this or any other diagnostic/repair issues, feel free to post in the help needed section.