I was told that its the same set up as KTM where you take the sprocket off, pull the sleve out, then there's a thin O-ring that you have to work off the shaft. Clean, grease and reasemble. After time you have to replace the seal in the case. You can do that fairly simple too.
I had the same problem as you, but at around 20 hours. I used some old 35mm film negatives (you know, what used to come back with your prints back in the pre-digital stone age) to clean dirt out from between the shaft and the seal. Just work the film strip in between the shaft and the seal (after removing the seal keeper), and you should get some grit out of there. I did this at about the 20 hour mark, and it hasn't leaked a drop for over a hundred hours since.
Patgas you live in Wales some very muddy conditions seal falures of all types are much more common in harsh muddy enviroments, especily so for fork seals when the conditions are icey. Dirt bikes lead A hard life knouing how to change A countershaft seal will serve well in the future.
seal i know how to change it done fair few engine rebuilds in past,was just wondering if this was a issue with 08s or a common problem
Friend of mine here in town just had the front output shaft seal fail too on his 08/TE-450. Replaced it, all is good now. Not the first time I heard of the seal failing on 08's
