Crankshaft Seal - getting the new one in! - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 17 (permalink) Old 07-16-2016, 08:44 PM Thread Starter
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Crankshaft Seal - getting the new one in!

2001 Honda RC-51 - coming home at night a couple of weeks ago, I heard a sound like I flung a rock or something. I ride for a little while and a few times it felt slick to me. As I found out, there was a good reason for that. Luckily, not too far from home, I came to a stop at a red light and noticed some smoke building around me. Looking around under the bike, I didn't see anything there, nothing on my boots or pants, so I pull off into a Home Depot lot under the street light and notice that I'm leaking fluid out of the rear of my fairings. Not a fast leak, but still enough that it was splashing my rear tire on the edges. Living about a mile from there, I basically nursed the thing home at about 10-15 mph to get it into the garage.

Long story short, the bike had been missing one of the screws that held in the tail under the seat since I bought it. Apparently, it was not missing, just hiding. It broke lose finally (almost 3 years later) and took a ride on the chain. Probably could have been WAY worse, but in the end, it put a nice gauge around the crankshaft seal (but only at the edge, so it should be no problem) and caved in the crankshaft seal. The leak was coming from the cave in.

After hours of work to get the thing out, I'm left with a new part I can't quite seem to get back into position. Does anyone have any tips to getting this thing in from the outside? I'm mentally drained after working on this thing for around 6 hours to get it out last night and I just don't want to smash it. I have lubed it up, but still can't seem to get it to go in.
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post #2 of 17 (permalink) Old 07-17-2016, 01:56 AM
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assume you are talking about the gearbox output shaft seal?
If so it is designed to be fitted with the crankcase split, you should be able to fit it by trimming away the raised bead and fitting it with some silicone instant gasket
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post #3 of 17 (permalink) Old 07-17-2016, 09:15 AM Thread Starter
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assume you are talking about the gearbox output shaft seal?
If so it is designed to be fitted with the crankcase split, you should be able to fit it by trimming away the raised bead and fitting it with some silicone instant gasket
The seal behind the front sprocket. I know the manual says to crack the case, which would be the easiest way to get the seal in, but I lack the space to make that an option. I also know bringing it to a shop would make it an overpriced job. Last time I was there for a tire change they hit me for 2.5 hours of labor and about double the price I was quoted.

I know it's not a high pressure area, so trimming would work for this, but my concern would be lacking something to keep it in place. I would hate to have that come out and get grabbed by the chain and sprocket. Has anyone else replaced this?
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post #4 of 17 (permalink) Old 07-19-2016, 07:37 PM
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Bring it to me motor out of bike and 1 hours time it will be ready to install back in bike its that easy to open cases slip that thing in and then close them back up.

You could go get some flexible gasket maker made for oil areas and trim the little raised ridge on the back side of the seal (it is there to grab the inside edge of the cases so as to not work itself out with the spin of the shaft), I would also gingerly with fine sanding drum or belt sander on really low speed maybe take off all the way around the outside edge of the seal no more than 1mm of suface and use that for the bonding thickness of the gasket maker (that would also make it easier to press it into place.

Part of the problem is you have to put considerable force on it to push it squarely and evenly both onto the shaft through the center of the seal and the outer portion of the seal into the bore cut into the cases, this mushrooms it and makes for not an easy job.

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Last edited by AMP1; 07-19-2016 at 10:11 PM.
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post #5 of 17 (permalink) Old 07-20-2016, 02:13 AM
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Bring it to me motor out of bike and 1 hours time it will be ready to install back in bike its that easy to open cases slip that thing in and then close them back up.

You could go get some flexible gasket maker made for oil areas and trim the little raised ridge on the back side of the seal (it is there to grab the inside edge of the cases so as to not work itself out with the spin of the shaft), I would also gingerly with fine sanding drum or belt sander on really low speed maybe take off all the way around the outside edge of the seal no more than 1mm of suface and use that for the bonding thickness of the gasket maker (that would also make it easier to press it into place.

Part of the problem is you have to put considerable force on it to push it squarely and evenly both onto the shaft through the center of the seal and the outer portion of the seal into the bore cut into the cases, this mushrooms it and makes for not an easy job.
wow you can tear down a motor and rebuild it in an hour, still you have the cost of new stretch bolts and head gaskets on top, going to come to a few quid
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post #6 of 17 (permalink) Old 07-20-2016, 08:53 AM
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wow you can tear down a motor and rebuild it in an hour, still you have the cost of new stretch bolts and head gaskets on top, going to come to a few quid
All I would do is split the case slip in the new seal and put back together.
Not time consuming to do just that

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post #7 of 17 (permalink) Old 07-20-2016, 12:21 PM
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All I would do is split the case slip in the new seal and put back together.
Not time consuming to do just that
How do you split the case without taking the heads off, removing the clutch and all the other bits and pieces?
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post #8 of 17 (permalink) Old 07-20-2016, 06:34 PM
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pretty sure the bottom case splits from the bottom
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post #9 of 17 (permalink) Old 07-20-2016, 06:49 PM Thread Starter
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AMP1, sent you a PM. Thanks for the feedback everyone. I can't tell you how much it hurts just to look at it in the garage and on a quiet night, listen to all of the motorcycles mocking me. Just got some fresh tires waiting to be broken in, finally fixed 1000 other random pieces, etc. Any tips on dropping the motor before I start?
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post #10 of 17 (permalink) Old 07-20-2016, 10:57 PM
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How do you split the case without taking the heads off, removing the clutch and all the other bits and pieces?
you would know how if you had ever got into the bottom end

enough said

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