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Thickness oil seal

Discussion in 'The Garage' started by Vww18, Apr 26, 2021.

  1. Vww18

    Vww18 XS650 Enthusiast

    Hi lads,

    A quite tough question !

    I bought a gasket oring kit and the oil seal behind the rotor is thicker in this kit (25/40/7) than the one I took out of the engine (25/40/5)

    My xs special is from 79.

    Do you know if there is an adverse effect in putting the thicker one ?

    Is it an improvement on the later version ?

    If needed, I can order the correct one but who knows ?

    Thanks a lot and I would understand if you say that this question is quite hard to answer !

    Cheers.

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  2. RustiePyles

    RustiePyles Semper Fortis XS650.com Supporter Top Contributor

    Does the seal stand proud of the seal counterbore? If not than you should be fine.
     
  3. RustiePyles

    RustiePyles Semper Fortis XS650.com Supporter Top Contributor

    25 40 5 & 25 40 7 are the actual seal dimensions FWIW.

    ID25 OD40 D5and/or7 so the 25 40 7 is 2mm taller than the 25 40 5
     
  4. Mailman

    Mailman Hardly a Guru Top Contributor

    There isn’t a lot of extra real estate where that seal rides. If the factory seal was 5mm in width, my concern would be that an extra two mm would put your sealing lip right at the edge, and the dust lip maybe even off of it.
    4A77E0FF-7977-4D4B-BE24-8F2EB2607CDA.jpeg
     
    gggGary likes this.
  5. 5twins

    5twins XS650 Guru Top Contributor

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    That SD-25-40-5 you're showing shouldn't have come from on the crank behind the rotor, it should have been a cam seal in one of the points/advance housings. The crank seal should be an SD-25-40-9. That new SDD-25-40-7 in the kit may be a replacement for the cam seal. Are there 2 in the kit? There was this thicker 7mm cam seal offered by the aftermarket but reports on it aren't that good. The cam doesn't stick out very much from the engine so that thicker seal may not sit on it enough to work.

    You'll notice in the chart below that there are 2 cam seals listed, 5 and 6mm thick. The first few model years came with the 5mm thick seal, then Yamaha switched to the 6mm thick seal. Now, they have gone back to selling and using the 5mm thick seal. Apparently a thinner seal works better here.

    [​IMG]
     
    Mailman likes this.
  6. bosco659

    bosco659 XS650 Junkie Top Contributor

    Nice oil seal chart, I’ll save this one. In the oil seal kit I purchased, there were two 7mm oil seals. They both were installed on the camshaft. No leaks yet. If it does, I’ll source 5mm seals.
     
  7. RustiePyles

    RustiePyles Semper Fortis XS650.com Supporter Top Contributor

    According to @5twins chart you need a 25-40-9 for the crank/rotor seal so even the 25-40-7 you have now is 2mm to short.
     
  8. 5twins

    5twins XS650 Guru Top Contributor

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    The crank seal is a confusing one. Older parts manuals I've downloaded list it as the 25093 seal and being 9mm thick. Later parts manuals that list the 25121 that superseded it call that one a 6-9, whatever that means, lol. MikesXS sells a 9mm thick replacement but one of the original part numbers it lists as to what it's replacing is 25090, the 5mm thick cam seal, lol. So, it appears you may find anything from a 5 to 9mm thick seal installed there.
     
    Mailman likes this.
  9. 5twins

    5twins XS650 Guru Top Contributor

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  10. Mailman

    Mailman Hardly a Guru Top Contributor

    Hey that’s a nice little chart! I snagged that one. ;)
     
  11. 5twins

    5twins XS650 Guru Top Contributor

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    I like charts, they're so easy to reference and compare the things listed in them. That's why I made that one up. I've got another "in the pipeline" pertaining to drilled disc hole sizes that I'll post up soon. I think you guys will like that one.
     
  12. Jim

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

    More seal info.....
    Koyo (industry leader in seals and bearings) recommends packing grease between the two lips. This prevents spinning a dry seal on a dry shaft and possibly ruining the seal right out of the gate. It's a good "common practice" to make a habit.

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    GLJ and Paul Sutton like this.

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