Crank seal replacement

if you are sure seals are leaking you will have to split the crankcase.I just did this job on my kdx 200 89.I suggest you to do a pressure leak test at your local shop to be sure because it is an expensive job.BTW look under the flywheel cover ...If there is premix or 2 stroke oil this mean left seal is bad too. If you split the cranckcase you must do that-----This is a jdbrush (member)tip

you might want to check on a common problem there was on the 89-94 kdx's with oil in the ign. cover.You will have to take the flywheel and stater off and check the area around the seal ,there are 3 slots cast into the case, pg 7-6 in the shop manual far left picture.With a all or nail try to see if you can pick some aluminum from these slots ,if you can see steel under this then this maybe the problem.The steel material you see is part of the sleeve that is cast into the case and is what the crank bearings are pressed into.When the engine is started the two materials expand at different rates and you get a little bit of oil seeping between the case and sleeve.To repair this clean the slots as best you can with contact cleaner and fill the 3 slots with JB weld,you can lean the bike on its right side and this will make the JB weld stay in the slots,also check to see if there is any radial play in the bearings,just grab the end of the crankshaft and see if there is any up or down movement , if there is it maybe time for new bearings.Hope it is just a leaking case its a simple fix and can be done in a few hours, good luck.

look at this too
http://dirtrider.net/forums3/showthread.php?threadid=42317&highlight=oil+inside+cover

Tom,are you sure the crank seal is the problem.When a crank seal goes it will usually draw or suck the tranny oil into the crank area.Is the hose routed to the bottom of the frame or does it go to the front of the airbox,are you sure the tranny is not overfilled,check the oil level with the bike upright not on its sidestand.Have you done or had a leakdown test done on the bike?the leakdown test will tell you if the seal is gone or not and will save you some downtime and a few bucks.A tester is easy to make and you can use it on future 2-strokes,or you can take it to any bike shop and have it done.does the oil look clear or is it gray and milky after you ride this could indicate a bad water-pump seal?

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Tom, there are 2 different routes you can go in regards to the leak down test,you can take the guts out of a spark plug(if you already have not tried it you will never find a harder substance to remove than the ceramic part of a spark plug)you will have to plug both the intake and exhaust port. for the intake just get a piece of solid round bar (1 5/8")and tighten the intake clamp around it,for the exhaust go to the local auto store and get a expandable frost plug(1 3/4").The other way is to keep the spark plug in plug the exhaust port with the expanable frost plug and build a leak tester that will fit the intake port.It just consists of a low psi guage(0-30psi) and a schrader valve(you should be able to find one at your local tire retailer)and plumb the whole thing into a t-shape,sorry I have no way of posting a picture.You only need to pressurize the crankcase to 8-10 psi,anymore and the frost plug will fly out,it it should hold that for @7-8 minutes.If it does not then get some soapy water and use a paint brush and apply it to the suspected area.you can just put some spit on the tranny vent tube and if it bubbles you have a leaking crank seal.If the seal is the problem then you have no choice but to take the motor completely apart,you cannot replace the crank seals without splitting the cases,sorry.You can use a tire pressure guage but it is not very accurate and every time you went to test the pressure because it is so low it would continue to drop,with a mounted guage you can visually watch the pressure go down.Before you get into all this try to run the vent tube to the top of the frame,do not put it into the airbox but just zap strap it to the upper frame,mine goes into the front of the airbox and maybe running it to the bottom of the frame has something to do with the oil loss,because with the amount of oil that you are describing that you are losing I would think you would foul spark plugs if the seal was gone.Has the engine ever been apart and if so could the right crank seal have been installed backwards,I have never seen a 2-stroke engine pressurize the tranny with a blown seal.The most common symptom of a blown seal is fouling plugs,since as mentioned before the engine will draw the oil out of the tranny.The grooves that kdxquebec mentions are on the left side under the ignition cover,this would result in oil in the bottom of the cover. :think:

Just my 2 cents worth.My stepson had a similar problem way back,with a Husky 125.Come to find out,the oil he was using,had too much of a gap in viscosity.Like 5w-50(example),causing the oil to froth and come out the vent hose.We were told that this type of oil has too many additives to be used with a wet clutch.He went back to Spectro trans oil and never had the problem again.
Just a thought.

isnt thier a gasket in their designed to break when the oil is overfilled?