Countershaft/Sprocket seal leaking on '12 250R

[Novascotiarider]

So I noticed some oil on the frame under my sprocket/countershaft. I had just cleaned my bike and lubed the chain so I figured it was just excess chain lube. After cleaning it and the engine case off and going for a short ride I found that the leak was coming from behind the sprocket. It is a fairly active leak.
The bike has low hours (around 50) and it seems odd that this would happen already.
I guess my questions are: 1. Is this a fairly common issue? 2. Can the seal be replaced from the sprocket side of the case? 3. Was this caused by a blocked vent on the transmission/where would this vent be located?
Thanks for the help!

[desertgasser300]

Originally Posted by Novascotiarider

So I noticed some oil on the frame under my sprocket/countershaft. I had just cleaned my bike and lubed the chain so I figured it was just excess chain lube. After cleaning it and the engine case off and going for a short ride I found that the leak was coming from behind the sprocket. It is a fairly active leak.
The bike has low hours (around 50) and it seems odd that this would happen already.
I guess my questions are: 1. Is this a fairly common issue? 2. Can the seal be replaced from the sprocket side of the case? 3. Was this caused by a blocked vent on the transmission/where would this vent be located?
Thanks for the help!

You can change it from the outside and I believe it is an oring

[Jakobi]

I'll take some pics for you mate. I have new seals here and my cases are about to be split. Good time for it. Common? I havent read about it and at 260hrs on mine it hasn't leaked.

[Cberg]

I had to replace one on a ktm 450, it is very common on the orange bIkes. I would think it would be a similar seal on the Gas Gas. It is real easy to do

[pscook]

Pair of o-rings held in by a spacer behind the sprocket. Don't think it's that common, but it's dead easy to inspect. Remove the sprocket, remove the spacer, and inspect the two o-rings. Replace as needed.

[GMP]

You can replace the seal if needed from the outside as well. More often than not its the orings, but still not that common like on KTMs. Did you change the countershaft sprocket from OEM? The tolerances must still provide a slight compression on the orings when stacked up.

[Rick]

Not a common failure area at all. I have had to replace one seal / o rings brushing in about ten years. Mine failed due to mud and wet grass picked into the counter sprocket area.
Check your transmission vent line to ensure it is not plugged up.

[GMP]

Its easy to tell if its the seal or orings. Remove the sprocket, its obvious if the leak is comming from the seal/sleeve. If its comming from between the shaft/sleeve, its the orings, as they seal the sleeve to the shaft.

[Novascotiarider]

I got the chance to give it a look today after work. Pulled the snap ring and sprocket off. Seems like I'm in for a seal and o ring, no other damage.
I will admit we were riding in some VERY muddy conditions last ride and I must have spun some junk around behind the sprocket. I'm running the stock Talon sprocket so that shouldn't be a problem.
Here's my next question, does anyone have the size specs for the seal and oring? I can order a GG set but would have to wait and there is a bearing/seal shop nearby that may have one in stock.
Thanks for the help all!

[Cberg]

Check the seal, size should be on it. Should have OD, ID and thickness dimension.