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What Causes Air Cooled Head Gaskets To Blow?

Discussion in 'The Garage' started by ReycleBill, Feb 27, 2011.

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  1. ReycleBill

    ReycleBill Part Time Tyrannicide

    As I delve into my first effort to replace a blown head gasket on an XS 650 I'm pondering. I know that steam is most often the reason water cooled engines blow head gaskets but because our XS560s are air cooled I can't help but wonder what causes them to blow head gaskets in the hope that I can prevent future blown gaskets.

    And please don't just say overheating is the cause because the result of overheating is most often piston seizure, not blown gaskets.

    Any informed thoughts?
     
  2. Jack

    Jack XS650 Junkie

    Engine studs are the main culprit,they're weak causing them to stretch and they're just plan to thin,along with that cushioning grommet they use to seal off prevent oil seepage past the studs.
     
  3. check and re-torque every year.
     
  4. ReycleBill

    ReycleBill Part Time Tyrannicide

    Jack and CDNTX650, Thanks, that's something I can chew on.
     
  5. ReycleBill

    ReycleBill Part Time Tyrannicide

    Next question: How do I get my hands on a set of high performance head studs?
     
  6. not sure of that, i just re-torque till i get constant readings after a re-build...then once a year.
     
  7. ReycleBill

    ReycleBill Part Time Tyrannicide

    Here's what I've learned thus far:

    The factory head studs are not up to doing the job. The racers used to make their own but the treating of metals is a little over my head-- does anyone sell high performance head studs for XS650s.

    Studs need to be kept at proper torque settings.

    Head gaskets on air cooled engines do not blow because of overheating. But, detonation (spark knock) will cause overheating and sometimes blown head gaskets. Detonation is caused by any or all of the following: timing advanced too high, Air-fuel mixture set too lean, too little air flow. We must be careful not to confuse cause with effect. Detonation causes blown head gaskets-- overheating is a common symptom (effect) of detonation.

    Detonation can also cause lots of things worse than blown head gaskets.

    Loud pipes might save lives but loud pipes kill perfectly good engines by hiding the sounds of detonation. (Makes me glad I got rid of that 2-1 header and megaphone that came on my bike when I bought it.)

    That said, another cause of detonation can be overheating. Detonation causes overheating and overheating causes detonation. Cause and effect sometimes intermingle.

    An oil cooler is a must. Check!

    Directing more air flow to the head is a must. A chin scoop and lowers attached to my new crash bars are planned.

    An oil temperature gauge would be smart.

    And finally, getting the engine out of the frame is a B&*&! when you've already got a hernia (busted nut.) I'm not looking forward to wrestling it back in.
     
  8. DLD1

    DLD1 Mechanical Stuff Nut

    Replace those sealing washers that have rubber in them with good copper washers, they will seal fine and hold the torque better.

    DLD1
     
  9. Travis

    Travis Staff Member Staff Member

    Are the head studs really too thin? I haven't heard anyone complain that they are having problems with them stretching or anything. :shrug:
     
  10. ReycleBill

    ReycleBill Part Time Tyrannicide

    In my opinion, the fact that they must be re-torqued most every year indicates they are less than they could be.
     
  11. ReycleBill

    ReycleBill Part Time Tyrannicide


    Now I must check to see which I ordered.
     
  12. This link has a ton of good information:
    http://xs650temp.proboards.com/index.cgi?board=EngineModified&action=display&thread=327

    Copper washers work very well on the large studs. Proper torqing is super important, and retorqing after the engine has been run. Make sure you have a good torque wrench.

    Removing or re-installing an engine is a 2 person job. It weighs 165 lbs................why would you want to injure yourself by doing it solo???? A couple of pipes and some nylon slings makes engine handling a piece of cake.
     

    Attached Files:

  13. ReycleBill

    ReycleBill Part Time Tyrannicide

    Great stuff there. I find it interesting that the subject of PCV (Positive Crankcase Ventilation) was mentioned as I've been wondering if this could be a possible cause (additional factor?) of blown gaskets.

    And the photograph will be remembered always.
     
  14. rwingsfan

    rwingsfan Xs 650 Dummy

    I put mine in and out by myself most of the time, really not that hard. You do not have to gorrilla it either. I put it on a jack rollit over beside the bike grab on and put her in laterally. Course no one ever confused me with a smart person. :banghead:
     
  15. I don't think so. I just check head bolt torque as part of my yearly look over.
     
  16. pulled my engine by myself, of course i had beer power!:D
     
  17. I pulled a Seca Turbo motor by myself. It was a heavy bastard.

    Depending on the thread pitch and length, you might check and see if some of the high perf dragbike engine studs from APE performance could be used. Might not be the cheapest route, but they are about the strongest studs you will find.
     
  18. XSLeo

    XSLeo XS650 Guru

    If you click tech at the top of the page and scroll down to homemade tools, browse the tools you will find several ideas on engine removal tools. I like the u-shaped, long handled tool that you hang from the ceiling. I think you could use it across a wheeled office chair too.
     
  19. ReycleBill

    ReycleBill Part Time Tyrannicide

    So does anyone know the thread pitch, length and other dimensions-- I've not yet opened mine up.
     
  20. Punkskalar

    Punkskalar Hugh's HandBuilt

    Bill,

    Contact ARP with the measurements you need. They will set you up with some headstuds that won't go ANYWHERE. I've used their studs on all kinds of things in the past that "stock" was not good enough for.
     

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