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Crank seals finally let go, full teardown necessary?

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Hey guys, the crank seals finally let go on my '02. Transmission was low, added some oil and went on a ride. Came back from the ride, transmission was low again and the crank oil was nearly up to the bottom of the fill port.

 

I believe there are two seals, one on the crank and one on the balance/pump shaft. Can these seals be removed from the transmission side just by taking the primary drive components off, or am I looking at a full engine disassembly?

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If the seals let go it's probably because the bearings are shot allowing the crank to take out the seals. Tear it down and put a crank and crank bearings in it.

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whoa... hold on. No way would i start off by splitting cases and tearing the trans apart.

there are a LOT of threads on "oil migration". search them.
clutch side cover off, basket off, drive gear off, replace the clutch side crank seal. Easy. Just MAKE SURE you put it in the right way. And i would get a later model seal to ensure it has the double lip, the earlier ones like 2004, were a single seal and would fail sooner. I have an 08, that i used same seal on my 04.

Balancer to come out and replace that seal, would need to remove the staor cover

 

i'm not saying your crank isn't bad, but without more info from you it would be premature to say replace it..

Edited by MELK-MAN
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If the seals let go it's probably because the bearings are shot allowing the crank to take out the seals. Tear it down and put a crank and crank bearings in it.

X2. If you want to change just the seals in it and not change the bearings, expect to change the seals often.

You'll want to at least give the crank a good look over.

Edited by HRC27

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The seals can be replaced by removing the covers as stated by MelkMan

I'd start with the left case cover and check the crank at the flywheel for any play.  You can figure out what you need to do from there.  

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Hey guys, the crank seals finally let go on my '02. Transmission was low, added some oil and went on a ride. Came back from the ride, transmission was low again and the crank oil was nearly up to the bottom of the fill port.

I believe there are two seals, one on the crank and one on the balance/pump shaft. Can these seals be removed from the transmission side just by taking the primary drive components off, or am I looking at a full engine disassembly?

Out of the 4 responses so far it appears that we have a tie in opinions. When you say the seals finally let go I have to believe you have a lot of time on the bike. If that's the case you could replace the seals and it should solve the issue for a period. If the bike has high hours you should do a complete tear down and replace the lower end bearings & seals. While the crank is out you can inspect it but since it's out you might as well replace it or at minimum have it rebuilt with a new rod & bearing.

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The bike is an '02 with who knows how many hours on it when I bought it in 2010. I put a Wiseco 12.5:1 piston in it, and put a TrailTech Vapor on it at the same time about a year after I got the bike. The Vapor says I've put 25 hours on the bike since the top end rebuild (that was 4 years ago, College keeps me busy these days, so I only get to take the bike out a couple times a month, if that). I probably put close to 75-100 hours on the bike in that year before the Vapor though.

 

The crank was still tight 25 hours ago, but I'll break out the dial indicator and give it a good checking over when I take transmission cover off.

 

Engine doesn't make any unusual noises, well besides the normal Honda CRF engine top-end rattle and clatter that every Honda 450 seems to make.

Edited by Lead Head

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A failed seal can be caused by radial play in the shaft bearing (as said above), or low oil not properly lubing the seal, or a stuck seal lip that had frozen to the shaft from long periods of sitting still, and then tearing it as soon as the crank turns again (like a stuck windshied wiper) 

 

When you pull the seal out, look for small bits of rubber stuck to the crank sleeve (stuck) look for grooves formed in the crank sleeve by the seal lip (not enough seal lube) and check for radial play at the crank for signs of bearing wear. 

 

I would suspect the crank is getting tired, and should be replaced for piece of mind for yourself. Just because a crank rod bearing shows no play in it, that doesn't mean that the roller cage isn't worn paper thin and ready to disintegrate at any time and lock up the rod.. 

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I have had much experience with an 03 that kept sucking the seal into the crank on the right side. The seal boss was loose enough the seal would be just shy of falling in. I replaced that seal a few times before I knurled the seal boss with a chisel and used anaerobic sealant on it. Every engine I rebuild I knurl the backside of the seal boss from the inside and have never had a problem since. Honda should have made a raised section at the crank side of the boss to stop that seal from sucking in.

 

The oil check valve in the bottom of the case is meant to block the piston from sucking oil from the oil sump side and make it dry sump in the crank area. It also stops aeration to the oil pump. Imagine how much suction happens when the piston travels up and no place to relieve the suction! It may have nothing to do with the seal wearing out on the lip side of the seal and the seal pulled in like so many before yours.

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