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crank seals --- which way do i install??

Joined
May 21, 2007
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#1
k, dumb question here.
Yes i should have taken pics before tearing apart 2 mos ago, but i forgot which way the seals go in my YZ250.. should i see the spring or not? they go in after the cases are back together, so i have made it that far...

thanks

rj
 

IndyMX

Crash Test Dummy
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Jul 18, 2006
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#2
Logic says to put the spring towards where the pressure is... I'd say to install the seals so that the spring side is towards the rod..
 
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Apr 26, 2007
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#3
That's a good question really. The flaw in your logic Indy is the pressure side varies with crank position. During part of the cycle the crankcase operates under a vacuum which puts the pressure on the outside. Because sucking air thru crank seals can be catastrophic to the engine, my instinct would be to have the springs facing outward. I grabbed the Clymer manual for my RM to find out for sure. Unfortunately, it's only further confusing things:

NOTE
For the right crankcase, install the seal
with the open side facing out. For the
left crankcase, install the seal with the
closed side facing out.
:whoa:

Go figure! Looks like you should consult the manual for your bike. If you don't have one, you really should get one. Otherwise maybe someone will check their manual for you.

Marc -
 
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IndyMX

Crash Test Dummy
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#4
the Manual for my Honda shows the spring side going towards the crank case on both sides.
 
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Feb 7, 2007
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#6
YZ250 manual (00 & 01) shows these seals installed with the springs faced towards the bearings.
 
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Oct 19, 2006
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#8
I have a 76 rm125 and low and behold the right seal is spring facing the crank and the right bearing in the clutch oil,better check the book!
 
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May 21, 2007
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#9
Thanks for all the great replies, I am going to install with the springs in. they do have a double lip, so there is a slight lip facing out. when i really thought about it, it occured to me that it would be a real pain to press the seal on the spring side, with no flat face to press against. i would almost surely damage the seal getting it in, now with the flat, i only have a 50% chance of dorking it up :^)
Thanks again for all your replies and time...
RJ