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SoCalMule

OEM Countershaft Sprocket RFS Motor

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  Hey guys, just returned from first ride after replacing chain and sprockets on my 07 KTM 450 exc and had a countershaft seal leak. Did some research and found that after market countershaft sprockets can be too thin compared to the KTM OEM sprocket with can lead to a seal leak. I did not know this. I purchased a new seal kit and OEM CS Sprocket and will let you know what the results are soon. Anyone have this issue in the past?

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There's been a lot of discussion about this in the past- I'd be very interested in your measurements of the two sprockets- I think it's a myth.

Did you order a new bolt and washer as well?

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Same thing happen to me on my 300 when I installed a different sprocket. Its common. I think it has more to do the difference in the balance of the two different sprockets. The old seal "settles in" on the old sprocket balance so when you put a different sprocket it gets thrown off and leaks. This is a common occurrence in the engineering field when dealing with shaft seals. I highly recommend using the technique depicted the following video. It makes the job easy and uses only common tools you probably already have laying around.

 

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Oh and I forgot to add the sprocket I have installed currently is not OEM. It's a Renthal 14 tooth (OEM is 13). The seal hasn't leaked since I replaced it over a year ago.

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1 hour ago, TexasDualler said:

Same thing happen to me on my 300 when I installed a different sprocket. Its common. I think it has more to do the difference in the balance of the two different sprockets. The old seal "settles in" on the old sprocket balance so when you put a different sprocket it gets thrown off and leaks. This is a common occurrence in the engineering field when dealing with shaft seals. I highly recommend using the technique depicted the following video. It makes the job easy and uses only common tools you probably already have laying around.

 

Thank you!!!! I will make the repair in association with this information that you have provided! 

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1 hour ago, TexasDualler said:

Oh and I forgot to add the sprocket I have installed currently is not OEM. It's a Renthal 14 tooth (OEM is 13). The seal hasn't leaked since I replaced it over a year ago.

 Yep, been running a 14T Renthal prior to the new 14T Renthal just installed; so, the leak is kind of weird. Found a 14T "KTM" CS Sprocket for replacement. I wonder If I can use the new Renthal 14T that is on the bike now with the new seal kit and have a dry CS? Might try it. 

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2 hours ago, paulmbowers said:

There's been a lot of discussion about this in the past- I'd be very interested in your measurements of the two sprockets- I think it's a myth.

Did you order a new bolt and washer as well?

No new bolt. I just purchased a new reusable thicker washer got one ride from it. 

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21 minutes ago, SoCalMule said:

No new bolt. I just purchased a new reusable thicker washer got one ride from it. 

Uh-oh.

DirtTricks? Like this one?

dirttrickswasher.jpg

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I change countershaft sprockets at least 6 times a year from 13 to 14 to 15 depending on where I’m riding. Never had a leak and I reuse the same washer over and over. I just rebend it a little. Your results will probably vary.

 

CiD

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56 minutes ago, paulmbowers said:

Uh-oh.

DirtTricks? Like this one?

dirttrickswasher.jpg

yep, sans the crack!

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34 minutes ago, Covered in Dust said:

I change countershaft sprockets at least 6 times a year from 13 to 14 to 15 depending on where I’m riding. Never had a leak and I reuse the same washer over and over. I just rebend it a little. Your results will probably vary.

 

CiD

I agree about using the washer over and over. Think the leak issue is due to the RFS motor CS seal tolerances...they are finicky maybe?

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39 minutes ago, SoCalMule said:

I agree about using the washer over and over. Think the leak issue is due to the RFS motor CS seal tolerances...they are finicky maybe?

I did the same on my 06 and it still doesn’t leak. Sometimes maybe you just get lucky

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Wait, Back to the Premise. I reject the concept of pressure on the seal needed to stop oil leak. The counter shaft sprocket has room to align with rear sprocket. I know the washer projects pressure but. Does the washer spin with Any of these sprockets? The pressure is on the inner race not the seal. The seal feels no pressure.

👀

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Good links, my husaberg (ktm)570 has always had a slow leak from counter shaft. Seal been replaced twice but just got full kit with washer and oring gonna give it a try, or burn it down

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2 hours ago, Bagstr said:

Wait, Back to the Premise. I reject the concept of pressure on the seal needed to stop oil leak. The counter shaft sprocket has room to align with rear sprocket. I know the washer projects pressure but. Does the washer spin with Any of these sprockets? The pressure is on the inner race not the seal. The seal feels no pressure.

 

Correct. The tightness of the bolt and washer holding the sprocket to the counter shaft has no effect on the seal. On some bikes, including my 300 XCW, the sprocket is held on by a snap ring which exerts no axial force on the seal or sprocket. The seal is made by the inner lip of the seal contacting the spacer bushing, which is forced onto the bushing by a band spring, and then an o-ring around the counter shaft contacting the inner bushing end and a raised portion on the counter shaft inside of the case.  

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Thanks for the vid Dualler.  Reminded me of that O-ring on the bushing. If that is broke, you are leaking.

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