Oil leaking behind front sprocket

So i recently noticed a build up of dirt and oil around my front sprocket. i finally got around to taking the chain off and pulling the sprocket off to see what was going on here. it looks like the oil seal has some dirt in it and is leaking slightly. i tried using a feeler gauge to clean out as much as i could to slow down the leaking, but i feel like this might have just pushed more dirt inside. Looks like i am going to have to replace that seal. I'm wondering if anyone has any idea what it's going to take to replace this? i have the service manual and there is not any real instruction (that i can find) for removal of this part. I was told by the bike shop to replace the bearing as well, looks like there is a bearing, an o-ring, then the seal, and a collar at the end (which is visible)


i am wondering how do i remove the collar? how do i remove the oil seal? and if it's possible to do it without pulling the whole engine off the bearing as well. i am hoping i don't have to pull the whole motor off, spring time just hit here and i wanna ride, i dont have time to pull this whole thing apart! But i digress, i need to figure out what to do, any advice is much appreciated.

Here's some additional info;

Part no. 25 31 26 need to be replaced (maybe only just 26?)

http://www.servicehondapsn.com/fiche_section_detail.asp?section=680107&category=motorcycles&make=YAMAHA&year=2008&fveh=18085

It is an outside seal so you can buy a new one. Pop the old one out and replace it from the out side, very easy. I carry an extra one with me on long rides. Don't ask me how I know !! Berwyn

If there is no play in the bearing I would just concentrate on the seal. That collar is a friction fit, it will pull out. You should be able to get the seal out without too much drama. Work from the shaft side though, don't try to pry it out from the case side. Worst case is you can screw a couple sheet metal screws into the bad seal and pull it out that way. I have success with that technique when leaking seals have been really troublesome to remove. Clean it VERY well before you install the new seal. Unless you have seal/bearing drivers, just find a socket that is close to the outside diameter of the new seal and use that to tap the new on in place. It's really a fairly straight forward job.

i got the seal off with out many problems, used a pick tool and worked my way around it evenly to pop it out. i bought a size 30 mm deep impact socket to seat the new seal in, and when i brought it home it was just a hair too small to clear the collar around the drive shaft. i went back to the auto parts store to exchange it for the next size up but all they had in stock was a size 33, so i grabbed it. it seemed to fit a little loose but i figured i could work with it. it took me quite a few tries to get the new seal on without it binding up or being on unevenly, the metal band inside popped out a few times while i was trying to get it back on, finally i got it on evenly and used the size 33 to seat it. with a couple wacks of the rubber mallet it was seated, i looked closer and it was a little crooked, the bottom was popping out a bit, so i hit it a few more times and tried to get it as even as i could. i couldnt get it perfect with the socket so i grabbed a tire iron and pushed in the bottom side to make it all even.

it looks like it seated evenly, but where i am concerned is that it seems to be pushed in a bit further into the case than the one i took out, i dont recall there being any type of lip to stop it from hitting the bearing that is behind it. im worried it could be making contact with the bearing and i don't want it to wear those out, or to continue leaking.

so where i am at now is;

should i just ride it and see if it still leaks?
should i order another seal, pop out the one i just installed and try reinstalling with a size 31 socket (the size i think would fit perfectly) is there any way i can remove the new seal without damaging it? (i really dont think that is possible)


anyone have any advise on my situation? i appreciate any input.... here are a couple of pics i took, one with the seal out and another with the new seal in. you can see how much further it is pushed into the case than the previous seal.

I wouldn't worry about it. In fact, it might be better if the area on the spacer was slight worn. Now the new seal is resting on a "fresh" surface.

i'm also worried about it not being in there completely even. is it possible for it to pop out while i was riding if it wasn't or would it just leak a little? i don't want it to come out and spill oil every where, or have the bearing get contaminated with dirt.

sorry for all the questions, i'm just trying to make sure i am doing the right thing here, this bike is my baby and i dont want anything to happen to her...

Sometimes it take the old seal and use it to seat the new one,gently.

Crankcase pressure should prevent dirt from getting to the bearing if it does leak. My guess is if the seal is slightly crooked it will work fine for awhile but won't last as long as one that was square.

Ride it and see.......

Just wanted to update and let everyone know that the seal has not leaked at all since I've installed it. It's been about 200 miles and I've done some rough riding to really put it to the test; two up in the woods, towing out my buddys drz out of a mud pit, and hitting 90 down the road and she has held up fine. Anyone else having the same problem I would encourage you to do it yourself and save some money. It was not that hard and the seal only cost 12 bucks! Thanks for everyone's input. Much appreciated!

Glad to know you got it sorted.


I've seen a few cases of leaky counter shaft seals caused by chain tension too tight. Not saying this was the cause in your case, but just sayin.... Chain too tight puts a lot of undue stress on the counter shaft, stretching chains, ruining bearings, and popping seals. Happened to me once, many years ago. Always better to have a chain that is too loose, than too tight.

Mine is leaking just a tad bit "not too bad though", I think I will give a try at replacing this seal. Dumb question maybe....but do I need to drain the oil?

You don't need to drain the oil. To recap my experience, I used a pick set to pry out the old seal. Picked it up at home depot for 4 bucks. It took a lot of force to pop the seal loose. Just make sure you work from the shaft side not the case side and work around the seal in increments. Be sure to put a little bit of oil on the new seal before you slide it back on and try to keep it even or it will bind up. And I believe a 31 mm socket will fit perfectly. I used a 33 and it was on the large side. Other than that it's pretty straight forward. Good luck

Thanks for the advice, I have new chain and sprockets coming so this sounds like the perfect time to replace this seal! Would you happen to have the part# for that seal?

Pokey wrote:

Thanks for the advice, I have new chain and sprockets coming so this sounds like the perfect time to replace this seal! Would you happen to have the part# for that seal?

Part number 93102-32480-00

Good luck!