Rear main leak...or ???

Discussion in 'Airheads' started by woodly1069, Jan 6, 2013.

  1. woodly1069

    woodly1069 Long timer

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    Ok fellas I have pulled my old R75/5 all apart for more reasons than just one but this is on the list to repair. I have had a small leak and assumed it was the rear main. After pulling things apart I really dont know if the main was leaking at alll. I will replace it but it looks to me as if this lower plate may be the actual culprit, what do you think?
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    I know it's hard to see but the main seal looks in tact. Could it be the lower plate seal also?
    #1
  2. JonnyCash

    JonnyCash turd polisher

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    From your pictures, I would say you're right, it's the oil pump cover. There's an o-ring under that cover. If it were the rear main, I'd expect to see oil thrown all around, not just down.
    #2
  3. disston

    disston ShadeTreeExpert

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    It looks like that is the original rear main seal. Make sure you change it. It has served well but it's time to go has come.

    The oil pump cover O-rings do go bad and leak.
    #3
  4. Brun

    Brun Been here awhile

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    And do replace the transmission input shaft seal as well.
    #4
  5. woodly1069

    woodly1069 Long timer

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    Will do, just as I expected! THANKS GUYS!
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  6. jackd

    jackd Long timer

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    Maybe someone has changed the rear main seal in the intervening time since the bike was built - it seems to be dry as a bone and who knows what age it is? Personally I wouldn't go farther than changing the oil pump cover seal - that seems to be a logical thing to do. But then I don't like finding more work than I have to. Your call.
    #6
  7. Kai Ju

    Kai Ju Long timer

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    Did you block the crank ? Please say yes.....
    #7
  8. woodly1069

    woodly1069 Long timer

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    I think I will change the rear main as well as the oil pump plate seal; hopefully that will do the trick. As far as blocking the crank I am unfortunately in the dark, what do you mean?...please advise.
    #8
  9. ozmoses

    ozmoses Ride On

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    #9
  10. ignatz72

    ignatz72 call me iggy

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    Oh boy...
    #10
  11. woodly1069

    woodly1069 Long timer

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    OK call me stupid, I'm sure the thing rotated at least 90 degrees but I marked it and put it back where it was when I started. How does it come off the thrust bearing? I don't understand...isn't the thrust incorporated into the mains?
    #11
  12. ozmoses

    ozmoses Ride On

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    You're not stupid. Read the link I provided, all the info is there.
    #12
  13. woodly1069

    woodly1069 Long timer

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    OK thanks
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  14. jackd

    jackd Long timer

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    All is not lost. Pull the front cover off the engine (by the alternator) and see where your alternator brushes presently are running on the rotor slip ring. If the crank has slipped ahead the carbon brushes will be contacting to the rear of where they usually locate. If they are still running in the same spot as usual then the crank hasn't moved and the thrust bearings have not come off their perches. If that's the case, then now is the time to block the crank at the front of said alternator.

    If your level of experience is limited with these machines then maybe you should take a pass on doing the rear seal and stick to the oil pump cover.
    #14
  15. ME 109

    ME 109 Long timer

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    Some good detective work there jackd.
    Those dowels/pins that retain the thrust washer are about three mm long from memory.
    #15
  16. supershaft

    supershaft because I can

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    That oil could not only be from the tranny input seal but it could also be from the clutch rod. You need to look at ALL the possibilities. It might be from the RMS too. I can't tell from those pictures. If that isn't the original seal it is the original type. The later types are SO much better. I would replace it. I would be tempted to replace that original oil pump cover for the same reasons. Plus it very well could be a big source of the oil.
    #16
  17. ME 109

    ME 109 Long timer

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    My later type oil pump cover sent me on a freakin' wild goose chase when it developed a hairline crack in the top left counter-bored hole.
    It presented symptoms of a leaking rms or worn guide ring or guide ring o-ring.

    I was advised (by GSPD) to run the motor without the tranny and clutch installed. Bingo! the leak identified itself almost immediately.

    The earlier angled counter-sunk type covers could not present this issue imo.

    I am proud to be the recipient of never before heard of airhead problems. True pioneering :D
    #17
  18. Beemerguru

    Beemerguru Beemerguru...G/S guy

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    Make sure you chase out the bolt holes for the oil pump cover. Previous owners/mechanics may have used Locktite to hold the bolts. Since the torque is only about 7lbs, any interference means the cover isn't seated..and will leak...again.

    Actually, I think you should use some blue so the bolts stay in place.
    #18
  19. supershaft

    supershaft because I can

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    I always heat them up in case some numnut has put red loctite on them. I always chase those threads. Not with a cutting tap but with a thread cleaner or a roll tap.
    #19
  20. ME 109

    ME 109 Long timer

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    Ah, the joys of having the same motorcycle for coming up twenty years.
    I know exactly what the numbnut has done.:lol3
    #20