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Front countershaft leaking oil

13K views 7 replies 4 participants last post by  ktmbmh  
#1 ·
My 08 300 XC is leaking oil at the front countershaft. Not from the dust seal but through the splines on the countershaft. I was running a Renthal sprocket then talked to the dealer and he suggested running the stock sprocket since these are set to KTM tolerance on the back space. I replace the spacer an o-ring when I did this swap. It didn't leak until I rode it. I have replaced the spacer and o-ring twice now with no luck at stopping the drool and have run it for the last 60-70 miles like that but sooner or later I'm going to pay the price. I understand the purpose of the o-ring to seal the internal fluid from leaking from behind the countershaft bearing through the spline. The shaft should have 1-2 mm of smooth surface where the bearing resides and the o-ring would seal but I can not see a shiny surface the the o-ring would mate too.

Is my last resort splitting the case here? Or am I missing something really bonehead, I mean how difficult could this be?
 
Discussion starter · #4 ·
Thanks for the input.
Bajadog, I have already been down that road, the leak subsided a bit but still leaked. Aj300, I never thought of your solution.

Went to the dealer today and we both came to the conclusion that the front countershaft splines are wore out because the sprocket has a 1-2 mm rock to it with the stock spacer and o-ring. In lieu of replacing it it went with a 19.5mm x 3 thick o-ring, it's a smaller diameter but thicker than stock with the hopes this would provide the back space pressure required to keep the o-ring tight to the backside of the bearing. This appears to have worked and will wait to see what the longevity of this trick will be.