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Main-shaft Crank Seal Question

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I'm rebuilding a 1982 YZ 100 from the bottom up...it was a "bike-in-a-bucket" thing. All parts are accounted for though.

So I'm at the place where the crank seals go in. This should be one of the easier steps in the whole process. I got OEM seals for the bike. What I'm finding is that as I crank down the torque on the nut to the main gear on the shaft, it (obviously) mates quite tightly with the seal...so much so, that the crank turns with some difficulty.:smirk: AND I haven't even torqued it to spec yet. Is this normal, and will the seal sort of "break-in over time"?

Here's a pic, and yes, I did drive that seal in a little further than what you see in the pic.

4.jpg

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The factory seals usually have fairly stiff Teflon lips. It has been a few years, but I recall there being noticeable drag. Did you apply a good grade of moly grease or assembly lube to the lips? It is sort of a must for decent seal life. I usually pack the area between the lips with moly based assembly lube, they tend to last a lot longer this way. Works for transmission and four stroke seals as well. Did you polish up the seating surface with 400 grit wet or dry paper? Don't forget that step.

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The factory seals usually have fairly stiff Teflon lips. It has been a few years, but I recall there being noticeable drag. Did you apply a good grade of moly grease or assembly lube to the lips? It is sort of a must for decent seal life. I usually pack the area between the lips with moly based assembly lube, they tend to last a lot longer this way. Works for transmission and four stroke seals as well. Did you polish up the seating surface with 400 grit wet or dry paper? Don't forget that step.

I cleaned up the surfaces with some zero-"grit" steel wool (cleaned all the residual nasties out). I haven't tried using some assembly lube, I'll give that a whirl. The stiffness of the seal is bothersome, and hoping that it safely "breaks itself in" without damage or resultant loss of hp.:smirk:

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I cleaned up the surfaces with some zero-"grit" steel wool (cleaned all the residual nasties out). I haven't tried using some assembly lube, I'll give that a whirl. The stiffness of the seal is bothersome, and hoping that it safely "breaks itself in" without damage or resultant loss of hp.:smirk:

The wet or dry paper is the same as running a hone over the cylinder walls before new rings. It gets rid of the polished groove left by the old seal, and gives the new seal a nice surface to seat against. Steel wool won't do it, and might even leave a few fibers to cause other mayhem.

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