KDXRIDER.NET

I've had this leak ever since I got my KDX, and one of the things that irritates me most is a leaking seal. I've replaced the seal 2 times, and the O-rings behind the collar 3 times with a thicker O-ring in hopes of solving the problem and it still leaked. So I recently replaced the whole thing with brand new OEM parts: the 2 o-rings, collar, and seal, applied a thin film of grease onto the collar, and put silicone around the outside of the seal after it was pressed into the casing in case it's leaking from the outside. Rode for about 15 minutes and parked it to find that it's still leaking. What could possibly be the problem? I'm sure a thin film of grease on the collar wont cause it to leak?

The seal is supposed to have high temp grease (the red stuff) put on the lips so, no, I know that isn't the problem. If you have replaced the seal, collar, and the two O rings then there is only two things left that I can think of, the output shaft bearing (sprocket side) or the output shaft bushing (kick side) inside the cases. You gotta split the cases for either one so you might as well do a bottom end rebuild if your going that far in to it. I hope I'm wrong, and maybe someone else has another possibility to share, but I think that is what is causing the problem.

Sometmes the recessed area (where the seal is pressed into) needs to be coated with gasket sealer first. This prevents oil from being able to escape around the seal. I always do that on my crank seals as a precaution, for example. Putting a sealer over the seal after it is inserted won't stop a leak.

I plan on going into the transmission and bottom end in about a year or so when I can send it to a shop, but I really hope that isn't the problem. And I did put some gasket maker around the seal before installation and its still leaking

Try a to move the shaft up and down and forward and backward looking for play in the bearings as mentioned.

Another thing to try is to replace the front sprocket with a different brand. The thickness of the sprocket sets the preload of the collar into the o rings so if the sprocket you have is a little bit thinner or worn enough around the snap ring and collar surface you may not be putting enough pressure on the o rings. You can also try wiggling the sprocket in and out to see how much play is there.

The sprocket sizing is a good point, but it looks like it's leaking from the outside of the collar from the seal itself, I'll give it another look. The output shaft has no play at all, so it looks like the bearing and bushing are okay

The area that the leak is in can be very hard to tell EXACTLY where the leak is coming from. With the sprocket spinning a million miles an hour it can fling the oil every where. Maybe you could clean everything up and tip the bike on it's side to see if it will drip without it running to get a better idea of what the problem is.

Also, just because you can't feel any play doesn't mean there isn't any.

rbates9 wrote:Try a to move the shaft up and down and forward and backward looking for play in the bearings as mentioned.

the output shaft can move inwards and outwards, but I can't feel the slightest bit of vertical or horizontal play

Mine is a 1987 model and only had one o-ring when I disassembled it. I figured maybe you were going about it wrong by using two o-rings so I looked up the parts fiche for your 1989 model and it does in fact show two o-rings. Otherwise, the assembly looks identical as far as I can tell. Maybe your collar is chamfered differently from mine but I can tell you that mine looks like it would leak like a sieve if I used two o-rings. It seems that you've tried everything else so I would suggest trying just one o-ring and see if your problem goes away.

KDXrider1989 wrote:

rbates9 wrote:Try a to move the shaft up and down and forward and backward looking for play in the bearings as mentioned.

the output shaft can move inwards and outwards, but I can't feel the slightest bit of vertical or horizontal play

In and out a little is fine. How bad is the leak that you are trying to stop? To me after I replace the bad parts and the problem is still there it comes down to is it really worth any more effort. It is nice to have a nice clean, dry bike but it might not be worth trading you sanity for. I have a slight leek / seep from the sprocket as well. I lost interest in fixing it after I replaced all the parts ( O rings, sleeve, seal, sprocket, snap ring) twice and have it only last a few rides before it was damp again. I wash my bike after every ride so I can get rid of the evidence and pretend it was never there.

Mine also leaked even with new seal/oring/bushing, there was some in/out play too, so I shimmed behind the sproket using a big circlip to get no more play.. It didn't leaked since ( May 2012)

rbates9 mentioned that an aftermarket sprocket might be a little thinner, and I do have a Renthal up front. Ever since I replaced everything, I havn't tried to put a washer behind the sprocket. The retainer ring that holds the sprocket in place is pretty easy to put on with all this new stuff, so hopefully this works

took a closer look at my countershaft seal today, here it is:





it almost looks like its leaking from those 3 dark rectangular things around the seal (can this happen?). The countershaft is not oily, nor is the collar or the lips of the seal. So I know now that the seal and the O-rings are not the problem. Sorry for the low-quality pictures, my camera can't focus up-close for some reason

I recall reading a thread about a year ago regarding those rectangle things leaking oil including a repair procedure. Something about the casting behind those areas on thumpertalk I think. I'll try to find it again if I can. You might want to do some searching on the subject.

that would be much appreciated

Not as detailed as I remember but miight help out.

http://www.thumpertalk.com/topic/867172 ... try9015948

I've had bad luck with JB weld, it never works for the stuff I wanted it to. I don't know if it will patch up something like this

Maybe take it in to a good TIG welder and have him just make a small bead over each of the areas and then grind it down for clearance?