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cases split -- can I replace crank seal without removing head?

Discussion in 'The Garage' started by DogBunny, Apr 4, 2018.

  1. DogBunny

    DogBunny Motorcychologist

    My cases are split so that I can work on the tranny, but the whole top end is intact. The literature says to replace the crank shaft seal when you split the cases because that's the only way it can be done, and you won't get the chance again. But that same literature is referring to an entire engine rebuild complete with head and cylinder removal.
    Does anyone know for sure if you can replace the crank seal without removing the head? Specifically, will the cam chain allow me to lift the crank shaft enough to remove and replace the seal? I'm thinking the cam chain probably has some slack from use, and I can back the cam chain adjuster way out. But if it's not possible I don't want to disturb and possibly mess up the old seal.
     
  2. Jim

    Jim Beyond the edge, is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    With the tensioner loose, it shouldn't be a problem. Keep in mind, the crank bearings have alignment holes. Make sure the outer races slip back into the alignment pins on the case.

    Edit: if it was me, I'd replace the other seals (clutch pushrod, shifter, and tranny output) too while I have it apart.
     
  3. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    That left crank seal should be 93102-25121 (SD 25 - 40.6 - 9).
    See if your seal shows the same (SD 25 - 40.6 - 9) markings.

    There were subtle differences in the early 70-73 seals, including the retention ring meant to fit in the retention groove in the case.

    XS-LeftCrankSeal.jpg

    Hard to tell from online pics, and parts manual excerpts, but it looks like the later seals may not have the retention ring. See if your new/old seals have that retention ring, and matching markings.

    If no retention ring, should be easy to swap out.
    If yes, the crank will need to be lifted sufficiently to clear the retention grove/ring.
     
    Jim likes this.
  4. DogBunny

    DogBunny Motorcychologist

    Thank you!
    Yes, I will replace the clutch pushrod and the output shaft seals. I think the old ones are fine, but it's just too easy to do them now.
    I took care to completely clean and lightly oil the shift shaft before I pulled it through its seal, so I'm pretty sure that it is still good. But if it does leak, it can be replaced later with the engine in the frame.
     
    TwoManyXS1Bs and Jim like this.
  5. DogBunny

    DogBunny Motorcychologist

    The seal in both the donor and keeper engines is marked SD 25 40 followed by 9-L-1 followed by HS. No point 6 - 9 marking.
    The seal DOES have a retention ring. This, according to the translated German manual of Hans J. Pahl is why you can only replace this seal with the cases split. Yes, you have to lift the crank shaft enough so that the seal's retention ring clears its groove in the case.
     
    TwoManyXS1Bs and Jim like this.
  6. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Somewhere, buried in my notes, is a publication about changes to the various seal retention rings. OEM rings are shaped like a semicircle. An optional seal retention ring is shaped like a barb, allowing easier insertion without shearing off the retention ring. Do your retention rings look like semicircles, or barbs?
     
  7. DogBunny

    DogBunny Motorcychologist

    DSC02277.jpg
    I think this is what you are calling a barb. This is an OEM replacement ALS brand crank shaft seal with the exact same markings as on both my donor and keeper engines (also ALS brand) that I quoted above. Wet side to the left, dry side to the right. Beveled, so that you could theoretically push it in from the outside with the cases closed. Note the depression just outboard of the barb -- I guess for the barb to fold into while you push the seal in until it hits the groove in the case and springs back out, locking it in place.
    The ouput shaft seal and the push rod seal are exactly the same, beveled "barb" with a depression just outboard of the barb. However, I'll say this: I have replaced many push rod seals with this barb and depression just outboard of it, and I have sheared the barb off of every single one. Yes, I chamfered the case edge first. But, every one still sealed.
    I've replaced the output shaft seal from the outside too with the cases closed. I don't remember if the barb sheared off or not, (I'm thinking it didn't) but the seal sealed.
    I think the barb on the crank shaft seal has a better chance of not shearing than the push rod seal, were you to try to install it from the outside with the cases closed, due to its larger diameter. But even if that barb did shear, I think the seal would still seal.
    But clearly, all three of these seals install one heckuva lot easier with the cases split.
    I don't think the seal in the picture is optional, this is the factory specified 93102-25121 crank shaft seal for 1974 and up.
     
    TwoManyXS1Bs likes this.
  8. 5twins

    5twins XS650 Guru Top Contributor

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    Here's a little seal replacement tip I've been using for years, and I think it really helps. Once the old seal is removed, buff that area of the shaft clean and shiny with a Scotch-Brite pad. This won't remove any material from the shaft, just thoroughly clean and smooth it. This gives the new seal a fresh surface to work against. Believe it or not, the rubber seal lip will, over time, start wearing a small groove in the shaft. This will alleviate and correct that.
     
    delagem likes this.
  9. xjwmx

    xjwmx XS650 Guru Top Contributor

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    The crank doesn't have to be lifted to replace the crank seal any more than the push rod has to be lifted to replace the push rod seal ;)

    I have replaced mine with the engine in the bike. First note the depth of the seal. Next drive one of those beaked seal pullers into the old one and lever it out. Bevel the recess slightly with a pocket knife. Note the postion of the ridge on the seal and the corresponding groove. Coat edge of the seal with lube or something like motoseal 1. Use a 1 1/2" sink drain repair pipe (blister back at HW strore) to drive it in. Make sure seal stays level during the process.

    I did this going by this video by a member here.
     
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  10. xjwmx

    xjwmx XS650 Guru Top Contributor

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    PS. the Scotch-Brite pad is a necessary step on all seal replacements as far as I'm concerned. Don't know why but it works like magic.

    P.P.S. If you were replacing the seal with the case split and wanted to lift the crank a hair, just remove the chain adjuster and there will be enough slack to let you do it. When you finish, make sure the pins in the case top are in the holes in the bearings right. Once you've cracked those head bolts there are a lot of other things you could do to refresh the engine and in steps mission creep. There was an amusing thread about mission creep here once.
     
    Last edited: Apr 5, 2018
  11. Jim

    Jim Beyond the edge, is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Just speaking for myself here... but if I already had the case split (as in this case). I'd go ahead and raise the crank slightly to lessen the chance of damaging the seal.
     
    TwoManyXS1Bs likes this.
  12. xjwmx

    xjwmx XS650 Guru Top Contributor

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    Of course, but you would not remove the head to do that. Maybe loosen the chain. Realistically with the case split there will be enough play that you could easily push the seal in with your thumbs and not want to raise the crank anyway.
     
  13. DogBunny

    DogBunny Motorcychologist

    Thank you 5twins and wxjmx.
    Thanks for reminding me to polish the seal contact area on the shafts. I always do that with the push rod, but I might have forgotten with the output and crank shafts.
    wxjmx, good info, and interesting video. I have never seen anyone hammer a seal puller into a seal like in that video before. I guess the full 25 minute video would be good for someone who has never repaired anything at all before. Otherwise, skip the first 15 minutes, watch the next 4 minutes, and skip the last 6 minutes.
    Couple more things:
    Green Scotch-Brite pads are pretty aggressive, but 3M doesn't tell you how aggressive, and there are lots of imitators out there, so you really never know what you are getting.
    scotchbritechart.gif
    I prefer to buy Scotch-Brite pads on this chart, by the box, but you can buy single pads at Home Depot. My favorite is White 7445. It WILL NOT scratch anything, not even aluminum, brass or paint. They hold an incredible amount of dirt, and can be rinsed and reused repeatedly.
    Next favorite is Light Gray 7448, but it WILL leave fine scratch marks on aluminum and paint.
    Finally, I use Maroon or Brown, but I don't use these much.
    So, from less to more aggressive, I am using flint, silicon carbide, and aluminum oxide. 3M will not even tell you what the abrasive is in a green Scotch-Brite.
    Personally, I think a green Scotch-Brite is a bit aggresive for shaft polishing.
    Second thing:
    There seems to be differing opinions on whether or not to use sealant on seals. My belief is that it is incorrect to use sealant on seals. Hans J. Pahl does not use sealant on seals in the translated German manual. I don't think any of the other XS650 manuals ever mention using sealant on seals either. I think sealant makes subsequent disassembly more difficult, and adds to the clean-up before reassembly is possible. In my opinion, it is especially unnecessary on seals that are placed, not pushed into position. That would be the push rod, output shaft, and crank seals on split cases. When you are pushing seals in, I think an appropriate lubricant is helpful, but sticky substances, such as Yamabond, et al, are counterproductive, and just get wiped off as the seal pushes in anyway. The lubricant I like to use is:
    51LeHcnlTOL.jpg
    http://www.itwconsumer.com/userfiles/files/techdata-sheet/VC Tech Data/34000 TDS.pdf
    It starts out slippery, then becomes a non-drying, flexible sealant. I also use it on gaskets, depending on the situation, and I especially use it on gaskets with minor tears. I think this is a very similar product to Gasgacinch.
    However... I do wonder if the same motor oil that the seal is sealing against might be a better lubricant. Prime Seal contains ethanol, propanol, and methyl isobutyl ketone, and who knows what effect they have on seals. Yamabond also has weird chemicals in it.
    Opposing opinions encouraged.
     
    Last edited: Apr 5, 2018
    TwoManyXS1Bs and gggGary like this.
  14. DogBunny

    DogBunny Motorcychologist

    Yes, that's what I intend to do, just enough to get the seal off and on.
     
  15. DogBunny

    DogBunny Motorcychologist

    Something just occurred to me regarding using or not using sealant on seals: when you replace a seal from the outside at a point where the case halves meet (or cylinder head halves meet), there is potential for a leak at the two points where the two halves and the seal meet. A dab of sealant at those two points would be prudent. But if the halves are split, and you are placing, not pushing the seal in, you already have fresh sealant on the metal at those two meeting points, and no further sealant on the seal is required.
     
  16. xjwmx

    xjwmx XS650 Guru Top Contributor

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    The scotchbrite I was talking about is the green pads sold everywhere for household scrubbing, It's about like steel wool but doesn't shed. Yes, the imitators at about 1/2 price aren't good; about like rubbing the thing with random plastic.
     
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