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can i put an after market front sprocket on an 08 450sxf? i have been told that i cant and am getting ready to order a chain and sprockets so i just thought i would ask and see.

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you can, but one of the problems thru the years is the front counter shaft seal leaking. This is often due to an after market sprocket not being thick enuf to seal the system properly. Its your money. I would get a KTM factory part.

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I´ve used Ironman (and most of my buddies use Renthal) front sprockets on both my -08 & -09 450 SXF and haven´t had a sign of leakage to date.

The OEM sprocket / thickness thing is in the past (read : RFS engine) so use whatever FS you want.

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Ville, you have said this before about the sprocket issue is only for the RFS motor. I havent seen an explanation from you yet as to how the new motors differ. I see that both have the same compression system for sealing in the parts diagrams. You are the only one Ive seen say this. Please explain how the new motors differ and dont leak, I want to learn.

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I just put a renthal front sprocket on my 07 SXF and I started leaking oil out the countershaft immediately. I don't know if I got something in there during the install or what. I checked it against the stock sprocket and it looks the same to me, but I didn't measure it exactly. I inspected everything and it looks good, I've cleaned it all and put it back together with the Renthal, haven't had a chance to test it again yet. If it leaks I will try to stock one again and see what happens.

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I just put a renthal front sprocket on my 07 SXF and I started leaking oil out the countershaft immediately. I don't know if I got something in there during the install or what. I checked it against the stock sprocket and it looks the same to me, but I didn't measure it exactly. I inspected everything and it looks good, I've cleaned it all and put it back together with the Renthal, haven't had a chance to test it again yet. If it leaks I will try to stock one again and see what happens.

A friend of mine had a problem with his leaking oil and it turned out to be the big washer that goes on the outside of the sprocket. I guess after a while they can loose some of their "tension", he replaced it with new and no more leaky.

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Ville, you have said this before about the sprocket issue is only for the RFS motor. I havent seen an explanation from you yet as to how the new motors differ. I see that both have the same compression system for sealing in the parts diagrams. You are the only one Ive seen say this. Please explain how the new motors differ and dont leak, I want to learn.

I don´t know how and i don´t really care why. I just know it is so.My RFS´s (all of them) would leak if i bolted on anything other than OEM FS. The new ones (RC4) doesn´t seem to care which brand FS i run. It may have to do something with the RFS engines needing a precise pressure against the outgoing shaft so the seal could do its job. Or something like that.

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A friend of mine had a problem with his leaking oil and it turned out to be the big washer that goes on the outside of the sprocket. I guess after a while they can loose some of their "tension", he replaced it with new and no more leaky.

May just be so. Dave Hopkins ( a TT Guru) said something about that too. He had an easy solution for it too. Included a ball peen hammer,a big socket and some force, i recall . I will try that once i get a leak due to a use of an aftermarket FS. Or just buy a new washer. Time will tell. Untill now no leaks (this includes my -07,-08 & -09 bikes) so i don´t really buy the OEM sprocket theory.

The washer thing sounds plausible though ...

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I put the sproket on backwards once and didn't notice it until oil started leaking out. It's easy to do if you are not paying attention. The result is that the cupped washer can not apply pressure to the sproket and the sproket is slightly loose.

Since I did it, I have seen the same thing on several other bikes.

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Ok, the new bikes have the same type of system, but maybe the parts are different and working better now. Most people are saying they are not leaking as often as the RFS did so they may have figured it out as you say. Thx.

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All KTM's require sprockets with the correct thickness, even the newer bikes.

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Mine turned out to be a total rookie mistake. The spacer / distance bushing was in backwards, so the smaller diameter end was on the inside thus no pressure against the o-ring. The Renthal sprocket works fine, no more leaks.

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All KTM's require sprockets with the correct thickness, even the newer bikes.

Correct thickness ,of course but there´s a span on that measurement ( that wasn´t the case on RFS engines) because the OEM FS isn´t mandatory anymore.

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