Airhead pushrod tube seals

Discussion in 'Airheads' started by rudolf35, Feb 25, 2011.

  1. rudolf35

    rudolf35 Warped & Twisted Mind

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    This might be a silly question but why does one need to use a tool to seat the pushrod tube seal with a older airhead? I know I can make the tool with a 1/2" pipe but the reason escapes me - enlighten me.

    :ear
    #1
  2. crazydrummerdude

    crazydrummerdude Wacky Bongo Boy

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    I've never needed a tool for my seals.
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  3. squiffynimrod

    squiffynimrod maximum shrinkage

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    Wouldn't that be the metal collar (?) on the older PRT's that you could cinch down a bit if they were weeping? Newer PRT's had a brazed collar that if you tapped them would break and leak even more. Is this for the 71?
    #3
  4. Grider Pirate

    Grider Pirate Long timer

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    That's always been a very temporary fix at best. Spending a few bucks and a morning replacing the seals is a better solution. No special tools required, and it doesn't take very long at all.
    #4
  5. CurlyMike

    CurlyMike Formerly SaddleSoar

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    sent you a pm. Please check...
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  6. Hawk Medicine

    Hawk Medicine Coyote's Brother

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    Temporary fix? Yes but it's also a reasonable solution to a frequent problem.

    I've been able to reseal my PR seals using a seal setting tool and a hammer on many occasions and thereby extend the usefulness of my old seals for more than a year. It took maybe 1/2 hour to make the tool, the materials cost was zero, c clean bike? Priceless!.

    I learned the trick from a trained BMW mechanic, who would always tighten up his customers seals during a regular service stop, if they showed need of it. That way, his customers could put that job off until it was time to schedule more extensive repairs, thus saving them time and money, while it also saved him time and made him money!

    Nothing wrong with that!
    #6
  7. 4ad

    4ad ochlacrat

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    These seals wear from constant expansion and contraction during the heat cycles of the engine. If you compare a new seal to an old one you'll see the ridges on the base are worn completely smooth on the old one....no amount of hammering will do much good for long and MAY even pull the pushrod tube from the cylinder....a pain to replace....and involves an angry wife wondering what the f&%k a cylinder is doing baking in her oven and stinking up her kitchen.

    Besides...it's bad karma to hammer on an airhead.

    Go ahead and change em...takes a 1/2 hr per side..and thats if you're slow.
    #7
  8. durtwurm

    durtwurm Talented Amateur

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    New seals or old, put a hose clamp on the tube next to the seal. It helps keep them in place and prevents weeping of oil.
    #8
  9. Xcuvator

    Xcuvator Justa Venturer

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    I have been rewarded with years of service from seals that had been reseated. Like has been said, you can put the replacements in when you are doing more extensive service. If reseating doesn't stop the leaking, you are not out anything, go ahead and change them.
    #9
  10. Hawk Medicine

    Hawk Medicine Coyote's Brother

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    How are you going to remove a push rod tube from the jug by resetting the seals? You're putting pressure on a non-fixed keeper that presses against the seal but holds it's position through friction. The tube doesn't move with the keeper because they're not firmly attached to one another and you're only moving the keeper 1/16" to 1/8" at most anyway. :huh

    Still, Your statement got me to thinking, so I went out to the garage and looked some R90 and R100 jugs. My conclusion is that it's simply not possible to hammer or press a push a rod tube, out of a jug, while the jug is bolted to the engine. Even if the tube was loose you couldn't do it because the push rod tubes are too long and even if they weren't, the lifters and cam are directly in the path of extraction.

    I'm not making this up and I'm not trying to make this an argument... Please go look at some Airhead Jugs and explain how your scenario could be possible.


    As an aside: Last Spring my pro Airhead mechanic and I both tried hammering a correctly installed SS push-rod tube, out of a cold jug and we found it impossible to do. Those SS tubes go in so darned tight that you'd destroy the tube, the jug or both before you got em out. Also, with the spacers fixed on those tubes, you cant reset the seals with em anyway.:lol3
    #10
  11. fishkens

    fishkens Long timer

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    Folks, I may have missed this but it's important to stress that using a tool to hammer in the push-rod seal collar only applies to what, pre-1977??? bikes. After 1976??? the collars were brazed in place and hammering on them will make things worse.

    I believe that tapping in those collars was a reasonable solution on earlier bikes but no solution at all on later bikes.

    I know some of you know the precise dates so I'll leave clarification to yous.

    I just don't want anyone with a late model airhead thinking they can resolve pushrod tube seal seeping with a hammer. For those bikes the ONLY solution is seal replacement.

    Am I wrong?
    #11
  12. Yarddog

    Yarddog Been here awhile

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    I didn't use a tool...I just took some sage advice from more learned folks than I and laid some black RTV on em and snugged everything down...works fine...
    #12
  13. Boxer Metal

    Boxer Metal Mad Scientist

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    This is quite simple. The push rod tube is pressed into the cylinder on all 1970-1995 Airhead Boxers. Always give them a little tap after at the collar after you have rebuilt your top end. Push rod seals and the sealing area should never ever have any sealant or oil when the are being installed. As the rubber dries up and shrinks you will need to do this again. I have also had success when they weep cleaning the area with brake clean very well and tapping them in.
    #13
  14. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Funny you should say that, since the advice I got fifteen or twenty years ago was to grease them up so they slide on the tube. Grease them all over.

    So I've used Silicon grease since it's most compatable with rubber and plastics and doesn't dry them out. The ones I've done this way seal and don't dry up later - I never have to mess with them again.

    I agree not to use sealant, it doesn't work. And it's a total bitch to clean up next time around.
    #14
  15. Boxer Metal

    Boxer Metal Mad Scientist

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    Interesting. I was edgimicated 25 years ago by old German dudes and they always said clean and dry.
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  16. fishkens

    fishkens Long timer

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    Interesting. I've heard repeatedly that post-some 70's date that tapping the collar was not a god idea.

    No sealant is my understanding but tapping the collar varies based on age, or so I've heard.
    #16
  17. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Used to be that I'd put a faint smear of silicone sealant ("Blue Goo") on the pushrod tube seals when installing-- the idea was that it served as an assembly lubricant and allowed the rubber to slide and seat in it's cavity and then served as a secondary sealant. But you don't need to "lock" the rubber seal to the block with sealant, it need to remain flexible for the heating-and-cooling cycles of the engine. So the past few years, I've used only Silicone grease on assembling the seals. Even after several years on the bike, the grease still feels greasy upon disassembly.

    OTOH, my opinion is that whacking the tube collar with That Tool is not a good idea. Early Airheads have a movable collar, later ones brazed. You don't want to move a collar installed at a set distance to fix a leak/weep/seep caused by an old rubber seal. Repair the leak by renewing the worn seal. The quandry is when you put a new seal on a PRT with a moved collar, the moved collar can put too much pressure on the new seal, deforming it and causing premature failure. So is there a spec for moving the collar to the "new seal" distance? Nope.

    You can do the job fast, you can do the job slow, or you can do it half-fast... your option. :)
    #17
  18. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Exactly! The seals needs to stay in contact as everything expands and contracts with heating and cooling cycles.
    #18
  19. rudolf35

    rudolf35 Warped & Twisted Mind

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    I was not ready for all these replies. I will just use silicone grease and wiggle them in there; if they are needed! There is a slight amount of oil mist around the right jug PRT seals. So, I degreased the area and will test ride the bike for a week.
    #19
  20. 4ad

    4ad ochlacrat

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    #20