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Drive shaft oil seal replacement XT250H

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Hi all! First post, great community you have here.

I'm just getting back into riding with the purchase of a 1981 XT250. It's in fantastic shape for it's age with 4900 miles. Three kicks to start almost as a rule and saving $$$ on gas!

So I started commuting to work on it two weeks ago and must have been a bit too excited (aka rough) with it:banghead:. Got it home last friday and discovered it was spitting oil from behind the drive chain sprocket. I'm assuming I need a new oil seal there. Seems like an easy fix but I wanted to see if anyone can advise me as to any gotchas with this. I'm still going searching threads for this, but all I've discovered so far is that the Clymer manual doesn't go into detail about this replacement. My main concern is that I may actually have more problems than just a bad oil seal. Anybody been there done that with this sort of leak that can offer tips to save me from n00b mistakes? Are there other parts I should inspect for certain signs of failure? Also, I've got as far as removing the cc cover which appears to have been sealed over the magneto to keep it clean. What do I need to use to seal that up again or does it matter what I use?

Thanks much!

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Clean the area well.

Have good lighting.

Lean the bike over to the right-hand side against a wall.

Remove front sprocket.

Carefully drill two small holes in the oil seal 180 degrees apart (try not to bottom the drill bit out on the bearing behind the seal).

Use two suitably-sized sheet metal screws to thread into the holes just enough to get a good grip on the oil seal.

Alternately pull on the screw heads, working the oil seal out.

Clean the area where the oil seal sits without gouging the metal.

Put an O-ring in the sprocket shaft groove (where the sprocket retainer sits) to protect the new oil seal's lips upon installation and apply grease to this area.

Grease the oil seal lips.

Push new oil seal squarely into place.

The left-hand side crankcase cover uses a gasket.

Get a new one.

If the cover is full of goop, somebody was in there.

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Awesome thanks for detailed reply!

I can't seem to find an O-ring in the parts schematic. I notice now though that the service manual (I have one for a year earlier model) mentions fitting an O-ring to the drive shaft in the engine removal transmission section, but no info on size, etc. How do I go about getting the right O-ring?

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The O-ring is not a part of your bike, but is only put in that groove temporarily to protect the new oil seal against getting damaged from having to slide over the shaft groove.

It's a precautionary measure mentioned in the Service Manual.

Any O-ring that will sit in the groove yet still allow the seal to slide over will do.

Just measure the shaft diameter and pick up a couple at either a motorcycle shop or hardeware store.

When the seal is in place, disgard the O-ring.

Edited by YZEtc
spellin'

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I see!! Thanks for the explanation. It wasn't getting through my thick skull at all, even with the service manual. I'll let you know how it goes.

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So I finally got the new oil seal in the mail. I pulled off the drive sprocket and discovered the old seal had partially popped out - no wonder oil was spitting out. Wonder how that could have happened?

I installed the new seal, but it seems as if it is still leaking oil at the drive, although not spitting it out everywhere at least. I haven't pulled everything apart again yet to see what's causing that. 👍

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You might want to insure that the crankcase vent system is clear .

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Thanks for the tip on the vent. Checked the hose, no oil in it and it passes air freely when I kick it over. Will check the airbox tomorrow. If this is clogged could it create enough pressure to push out the seal even?

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It's possible . I've never seen it actually displace a seal , but if the seal wasn't in right to begin , then ...

And , 30 year old rubber does get hard and brittle from hot/cold cycles . When that happens , it shrinks .

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Hi, sorry to bring up an old topic, I've had exactly the same problem with the xt250 leaking oil from behind the drive sprocket.

I have managed to get the old one out (thanks), but cant seem to find a new one after searching for hours...where abouts did you find yours?

Any help would be appreciated, Cheers

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What is usually done over here is that if your local Yamaha motorcycle dealer tells you that they don't have one on their shelves, they can order one for you.

This takes a few days, on average.

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Bert, the yammay dealer should be able to help you as the bike originally came into the UK, I can get spares for my 90 Xt350 from my local yammy dealer, normally takes 2-3 days for them to come, have a look at the microfiche pic's for your bike on bikebandit.com and that will give you a part number as well, makes it even easier in the shop or if you phone it through. If your struggling then give wemoto a ring, may be able help

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