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  1. #1
    override's Avatar
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    Engine Rebuild - New everything, leaking at rear seals.

    Finally got the motor to the point of doing a leak down test and upon pressuring up to 10 psi to hold for 10 mins the rear seal pushed outward slightly and is leaking at the inner portion that seals against the crank itself. Crank is brand new, installed in an engine previous but never ran...Seals are from a Winderosa kit, installed correctly, greased during install.

    I did the test multiple times tonight and right at around 7-8 psi the seal begins to push outward. Each test I would push the seal back in, I took a soft blow hammer and tapped it in as far was it would go. Leak down test still bleeds off about 4 psi in 10 mins, 5 psi in about 15 mins.

    I am astonished that new seals would leak like this, you can pressure up the engine and put your ear up to the seal and hear the pressure creeping by......

    Question is what in the world would cause this and what should I do from here...I do not want to have to split the case again, I don't really have the time to go through all this again and after what I have spent on rebuilding this ski I am tempted to just finish the build and list it....I'm so frustrated anyone have any advice or thoughts?

    Here is the build thread and what I have posted so far, pic heavy but the bottom end build up is shown...It's in the last post.

  2. #2
    butterbean_29512's Avatar
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    Maybe those carbon steel roll pins are slightly too long and will not let the cases mate properly. If I had to split them again I would purchase the correct pins.

  3. #3
    override's Avatar
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    Quote Originally Posted by butterbean_29512 View Post
    Maybe those carbon steel roll pins are slightly too long and will not let the cases mate properly. If I had to split them again I would purchase the correct pins.
    Those did not go in the case, those where used for the jugs and also were grinded to fit slightly loose.

  4. #4

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    Looks like your seals are in right, easy to mix them up and they DO seem to come out then!

    Couple off points:
    as butterbean said, are the cases definitely mating properly?

    Secondly, I wouldn't use grease on the outside edge of the seals. Split the cases, pull the seals, clean ALL the grease off the outer edges and inside the casing grooves. Then smear 1211 or similar sealer on them and a small amount on the cases where the seals sit. Grease the inner lips and refit back together.

    Lastly try 5psi instead of 10, your gauge could be out and 10psi would be the maximum you would want in the cases when testing. I do 8psi.

    If if afer all that they still pop out then it's time to bin those Winderosa seals and buy new OEM. Aftermarket aren't all bad, I've used WSM ones with no problems, you just might have been unlucky with badly sized ones


  5. #5
    butterbean_29512's Avatar
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    Always level your mating surfaces with a bench stone before reassembly. You may have a burr keeping them from mating properly. Also, I have used several sets of SBT seals over the years with no problems. I put 1211 in the seal groove to ensure a tight fit

  6. #6
    quadzilla's Avatar
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    Hey there..

    As has been mentioned in recent previous posts..

    Get that grease OFF the outer edges of your seals.
    - A little bit of 1211 in the case groves and on the outer seal edges is also my preferred assembly method.
    - Absolutely make sure you do fill the grease channel in the center of the seals.

    Now then,. To quote Jules from Pulp Fiction.
    Jules: Hey, sewer rat may taste like pumpkin pie, but I'd never know 'cause I wouldn't eat the filthy motherfucker.
    That really does sum up my thoughts on using cheapo aftermarket seals and carb rebuild kits
    - for the few bucks more, go OEM all the way.

    I will say your build and work ethic seem 100% spot on.

    .

  7. #7
    butterbean_29512's Avatar
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    I know many people do not like the aftermarket seals, but I have used them and put 100's of hours on them with no problems. Even installed my first set wrong, with no problems. (They were glued in with 1211). I have enough confidence in them to use them again, but of course that's just my opinion.

  8. #8
    Almost's Avatar
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    I will be following this closely for sure. I just sealed my cases this weekend with oem seals but I followed the Fercho engine assembly which says to put grease on the inner and outer edges. I didn't put any 1211 in the groves obviously because that wouldn't dry with grease.

    Now im starting to worry. I should be pressure testing in the next few days and let you know how I make out.

  9. #9
    butterbean_29512's Avatar
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    I know you do not want to hear this, but leaving those seals in with grease around the outside is inviting a seal to pop out while running, and leaning out the rear cylinder. If you just rebuilt it, you know how much it would cost if you had a lean meltdown.

  10. #10
    override's Avatar
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    Thanks guys for all the responses! I have decided since the OP that I will pull the motor back down. While I have it apart I'll see about using the thrust washer I didn't have with the pro X Pistons, also getting the correct alignment pins for the jugs and I am going to go ahead and replace all the seals with OEM. Sans the grease on the outer portion and instead possibly a touch of 1211 on the outer. I'm still reading all the posts but next days off I will update this when I get back to the second time around doing the leak down. I have to have the ski ready and broken in by the end of my next days off so I got that for motivation. Lol

    Quote Originally Posted by butterbean_29512 View Post
    Always level your mating surfaces with a bench stone before reassembly. You may have a burr keeping them from mating properly. Also, I have used several sets of SBT seals over the years with no problems. I put 1211 in the seal groove to ensure a tight fit
    What do you mean by level the mating surfaces with a bench stone? The case halves sealed pretty good, it's just the rear seals (possibly front also) that were leaking.

    Quote Originally Posted by quadzilla View Post
    Hey there..

    As has been mentioned in recent previous posts..

    Get that grease OFF the outer edges of your seals.
    - A little bit of 1211 in the case groves and on the outer seal edges is also my preferred assembly method.
    - Absolutely make sure you do fill the grease channel in the center of the seals.

    Now then,. To quote Jules from Pulp Fiction.
    Jules: Hey, sewer rat may taste like pumpkin pie, but I'd never know 'cause I wouldn't eat the filthy motherfucker.
    That really does sum up my thoughts on using cheapo aftermarket seals and carb rebuild kits
    - for the few bucks more, go OEM all the way.

    I will say your build and work ethic seem 100% spot on.

    .
    Thanks man, I do take a lot of care on anything I put my hands on. I tend to be a bit OCD lol. That quote tho haha.

    On filling the grease channel, your speaking of the two holes that are kinda between the two seals on the top half? I assumed that was for oil to be able to get in and lube the seals.

    Any pics of what your referring to?

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