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346xp air leak

Discussion in 'Chainsaw' started by morbius18, Jan 11, 2019.

  1. morbius18

    morbius18 ArboristSite Operative

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    I'm rebuilding a 346xp and was pressure testing it. It had about 1/2 psi leak over about 5 minutes. I got soap water and a brush and put it around all the common leak points and didn't find anything. Put it around the crankcase gasket and found it.

    20190111_172853.jpg

    So, I dirkoed the gasket around the crankcase. Is air able to leak through the paper, or maybe just not a good seal? I used brake cleaner on a shop towel in both sides and applied a little dirko with my finger. These should hold pressure with no dirko, let alone adding it.

    Any thoughts?
     
  2. Ronie

    Ronie ArboristSite Operative

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    I think that 1/2 psi over 5 minutes passes the pressure test. From the 372 workshop manual,
    "Pump up the pressure to 80 kPa (0.8 bar).
    5. Wait 30 seconds.
    6. The pressure should not be less than 60 kPa (0.6 bar"
    But if I found any leak I would fix it. You could try putting vacuum to it and try sucking the sealant into the leak.
     
  3. morbius18

    morbius18 ArboristSite Operative

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    I just hate having any leaks, especially on a super clean rebuild with new oem p&c. I like to come back 20 minutes later and still have the same pressure. I ordered a new oem gasket.
     
  4. Trent Curtis

    Trent Curtis ArboristSite Guru

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    Does it pass vac test?

    And what Psi did you test to?
     
  5. sunfish

    sunfish Fish Head

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    I've never seen one leak there?
     
  6. JohnT34

    JohnT34 ArboristSite Lurker

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    I put a new oem piston and cylinder on a 346xp and didn’t change the crank seals
    Now I am going back in to change the bearings and seals as the sealed bearing on the clutch side has failed and scored the new p&c
    Moral of the story should have done the seals and bearings


    Sent from my iPhone using Tapatalk
     
  7. jltrent

    jltrent ArboristSite Operative

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    I always coat the gaskets with a little Yamabond when putting back together, especially around the engine compartment. I have not had one to leak yet and probably done at least a 100.
     
  8. morbius18

    morbius18 ArboristSite Operative

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    I do the same with dirko. I thought it was odd to leak there.
     
  9. jltrent

    jltrent ArboristSite Operative

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    I had an 026 that leaked at the case there. After starting to tear it down I noticed a case screw loose. I tightened it up and it still leaked. I guess the seal was bad then. Replaced and that fixed it.
     
  10. morbius18

    morbius18 ArboristSite Operative

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    It 'passed' both according to psi change over 2 minutes, but did not according to my standard. I used 7-8 psi on both vacuum and pressure.

    Rarely do air leaks get better over time. My thoughts are it will probably get worse. If that's the case, since the saw is bare crankcase and cylinder now and clean enough to lick, I'd prefer to do it now.
     
  11. Trent Curtis

    Trent Curtis ArboristSite Guru

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    Ya i agree with you..... sorry you gta open that twice. What a PITA!

    Crazy- I use the same method you do..... but I use permatex.

    Clean scrape case faces, then acetone the sealing surfaces. Apply permatex to both case halves before installing gasket. Haven’t had a leak..... YET:confused:
     

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