Crank seals

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muddertrucker
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Crank seals

Post by muddertrucker »

I`m starting to suspect my crank seals need to be changed because the trany oil is starting to dissapear incredibly fast and there is exessive spooge coming out the tail pipe.

Could something else be causing this?
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Post by KarlP »

Not really.

Does the exhaust smell like burnt tranny oil?
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Post by canyncarvr »

There are a couple of very good links to 'Splitting the Cases' videos and sites with pics on this board. Sounds like you might be in the market for a few new cool tools!

...here comes another '..no longer afraid...' moment!!!

A btw...but if you run ATF, what does it smell like if it's getting sucked in?

If it smells notably different (I would guess it might) you could run summa that, see if the smell changes.

Same would apply to GearSaver or any other oil that might smell differently enough to give you a clue you're burning it..or at least pumping it through the cylinder.

Good luck!

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Post by muddertrucker »

I'm runnin Amsoil synthetic 0w40. I'm thinking it might just be too thin. I'm gonna try regular 10w30 just like I use to before it started to leak before I take the engine apart.

Re:...here comes another '..no longer afraid...' moment!!!

Being a diesel mechanic engines don't scare me but breaking all the litle parts inside is a different story :mrgreen:
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Post by canyncarvr »

Yeah...your idea of 'liddle' is a 3/4" drive 2 1/2" socket. :wink:

About 'regular' motor oil...keep in mind that newer spec motor oils do NOT have the required elements for acceptable wet clutch operation. Spec'd oil is only up to SE.

Use a motorcycle-use specific oil (verified high in potassium, phosphorus, vitamins A-K and all the other goodies) or at least a 'motor oil' rated NOT past SE.

Yep..it does matter! Your clutch will thank you!

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Post by muddertrucker »

I use the term "diesel mechanic" but it's more like diesel/automotive/armored vehicles/mobile support equipment/anything else with an engine and or wheels mechanic.

I just use castrol gtx 10w30. It's always worked and had no problem with the clutch. The Amsoil is a motorcycle specific oil and I started having problem since I switched to it (maybe coincidence).
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Post by canyncarvr »

Regardless of how rare such-and-so a failure is...when it happens to you, you're lookin' at a 100% failure rate.

Crank seals on the KDX are hardy. Few riders (outside of 220 owners that have grenaded their crummy OEM pistons) have had problems with 'em that I've heard of. I'm sure it's happened..but it's not a common occurence...not a weak point on the KDX.

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Post by Mr. Wibbens »

whatever oil ya use make sure it donut say anywhere on the bottle: ENERGY CONSERVING

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Post by Colorado Mike »

before you buy case splitting tools, make sure you need them. I haven't looked at the KDX design, but my kid's YZ does not require the cases to be split to replace the crank seals. you need a magneto puller, and you have to get the clutch off, and I think the outer clutch cover.

Of course, this is a moot point on his bike because he grenaded the motor and I'm replacing the crank and most other things anyway. If your crank seals are really leaking, you are well on your way to being like him, so change them. :supz:
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Post by canyncarvr »

The KDX seals are fit from INside the cases. Crank seals that is.

The output shaft seal can be replaced from the outside. A recent thread with all sorts of neat pics from Jeb discussed that.

Still, doesn't mean you need a splitting tool. Harmonic balancer pullers have been used to split bike cases. That generally requires some fiddling with getting 'long enough' bolts of the correct size/pitch to work. The balancer itself doesn't come with suitable bolts. Not mine, anyway.

Still..there are other tools that are a huge benefit when it comes to putting the thing together correctly: An arbor press for seal/bearing placement for one...a correctly sized crank spacer for another.

The crank being a two piece unit, it don't make no sense to be squishing on the separated ends when the cases are squeezed together..and NOT bridge the offset at the big rod end. I'm sure it's been done often by many..and I'm sure I wouldn't want to do it that way.

imo and all that happy hs.

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Post by muddertrucker »

Re:The output shaft seal can be replaced from the outside. A recent thread with all sorts of neat pics from Jeb discussed that.

If my trany oil is dissapearing it's probably through the output shaft seal right? In that case my riding season might not be over :supz:
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Post by canyncarvr »

When you axed that question earlier, it was assumed (by me) that there wasn't a big mess elsewhere that indicated an outside leak.

If you have oil coming out via the output shaft, unless you bike is a total disaster of a mess, you'll see it.

In regard to crank seals...note Mike's thread..what happened on his kid's leaking seal bike.....

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Post by muddertrucker »

I completely missunderstood your thread. The parts in THAT thread were all replaced (I actualy got spares of each for next time it leaks), the outside leak was remedied and oil is still disapearing. By output I thought you meant to transmision. Could a plugged exhaust cause crank seal failure?
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Post by canyncarvr »

We're amiss, here.

The output shaft thread is HERE!

So..you replaced those parts, fixed that leak..and oil is still 'disappearing'?

In which case a reference to, 'If my trany oil is dissapearing it's probably through the output shaft seal right?' doesn't fit.

..which is the part you misunderstood. I think.

So, we're square up to this point? :hmm:



'Could a plugged exhaust cause crank seal failure?'


By 'plugged' you mean restricted I suppose. IF the restriction was so great as to allow combustion pressures to get back to the crank seals when the transfer ports were uncovered, I guess it would be possible. But...the bike would run SO crummy..if it ran at all, I don't think combustion pressure would even exist.

Simply put, I think not.

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Post by muddertrucker »

By pluged I mean that I forgot to remove the exhaust plug, started the bike and reved it a couple of times before realizing that the bogging noise was being caused by the plug.

Re:In which case a reference to, 'If my trany oil is disappearing it's probably through the output shaft seal right?' doesn't fit.

That's right it doesn't, because I wrote it before reading the referenced thread :oops:

Re:So, we're square up to this point?

For now :lol:
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Post by canyncarvr »

Seems on the odd side that it started at all. I would suspect there are some other leaks someplace...like the pipe to cylinder joint.

Kind of a btw..but you know how seal lips are generally 'tapered' some (you know this..said more for the casual reader who might not)? They generally fit a in a particular orientation. You can see that in the following:

Image

While a crankshaft seal would probably do a fair job of keeping oil IN the crankcase (if there was oil in the crankcase..like a 4-smoke), the shape of the seal is more intended to keep stuff OUT. There will be some positive pressure on the down stroke, but there is also considerable vacuum on the upstroke.

That sucking sound you hear in the airbox comes from someplace, 'eh?

THAT is the pressure (negative) you are protecting with crank seals.


That same seal will not likely be harmed if there is a pressure rise inside the case that causes a seal to be compromised. The seal 'wants' to go that way in the first place.

Besides...seals don't generally fail all by themselves. Something CAUSES them to fail..and that 'probably' is a bad bearing. The bearing gets wonky due to lubrication failure, lateral forces, or some harmonic problem. The seal cannot do it's job very well if the outside shaft diameter it rides on is moving in anything other than a 'perfect' circle. (all circles are perfect...by definition).

IF your crank seals are leaking, there is a good chance your crank bearings have 'issues'.

Back to CM's post......... :cry:

IF you have seals that are leaking. I don't know that they are or aren't.

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