Crankshaft Oil Seal

JohnScott

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#1
My '96 KDX is using transmission oil. I'm pretty sure the right side crank seal is leaking because I get a lot of smoke for about 10 minutes after starting on a full tranny. How hard is it to replace? Can it be done without splitting the case? What is the procedure?

Thanks.
 
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#2
Buy a manwell & work your way through it. All pretty easy stuff but best to have an experienced friend walk you through it & remember comments in the manual like ‘remove bolts & separate the cases’ take a moment to read but can take an age to perform. Sidenote, soft faced hammer/rubber mallet & be gentle, never metal hammer & watch what you are hitting, put that screwdriver down.

In my younger years I have tried to replace RHS seals without splitting the cases but wasn’t successful so have grown to believe that you can waste a lot of time trying to save time, do it properly.
(& replace both seals while you are there)

Its time you replaced the rings & cleaned the powervalves anyway?
 

JohnScott

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#3
Running a brand-new top end. Do you think it would be OK to hold off until the next time a top-end is needed?
 
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#4
No sorry, if you are sucking oil then you are going to be sucking air from the part of the seal that isn’t submersed which is dangerous.
 

MADisher

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#5
Yes, but...

It depends on how much you are sucking... If you are planning another top end this winter, and it's not bad to ride then have at it. (IMHO)

When the seals started to go bad on my RM it was still very rideable for a few months. But then it did deteriorate rather quickly. Sucking air wasn't the problem, fouling plugs from tranny oil was. Oh say about ever 20 minutes like clock work and it smoked like a chimney.

Then again, unless you do it yourself you won't find many places that will do internal engine work (i.e. split the case) around here until winter mos anyway.

David's proably right though... :)

-MD
 

dhoward

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#6
Riding with a bad seal is a nasty accident waiting to happen.
I would replace the seal as Mr.Trustrum reccomends.
:)
 

JohnScott

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#7
I understand that running with a leaky seal will suck some of the tranny oil out. Other than carbon and fouling, what kind of negative effects will this have on the top end?
 
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#9
S’right, the oil isn’t the problem, though may start to foul plugs. My real concern is that the gearbox is only part full of oil so you will suck air as well (remember the bottom end is a pump & the gearbox is vented). This air will weaken the mixture & if it gets lean enough will seize the top end. Remember that nice new top end you just forked out on?

Makes the decision easier huh? Don’t worry its not that hard once you are into it. You could always strip it down as far as you are comfortable & find a shop to complete the rest.
 

JohnScott

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#10
Thanks guys. You're right. I'll tear into it in a couple of weeks - I'm just afraid of what else I might find.