Need new headbolt/is my piston burned?

Discussion in 'Frame Mounted Engines' started by Keepthedrivetommy, Mar 12, 2008.

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  1. Anyone know where I can buy a new headbolt, just the headbolt? I stripped the top of one of them, and the nut wont screw on now. I figured that it wouldnt be safe to ride with one nut missing, so I didnt ride.

    Also, once I get one, how do I tighten it as much as possible without stripping the threads?

    And finally,
    I checked my piston, and the top of it is mostly covered with oil/gunk. Some of it can be scratched away with a fingernail while most of it has hardened. Is this how the piston is supposed to be?

  2. mickey

    mickey Guest

    When I broke my cylinder stud, I had to buy stainless threaded rod from a local fastener shop and cut it with my dremel. On the plus side, a meter of 6mm rod cost about $4 and can be used to fix broken mounting studs as well. They're all 6mm rod on my Kings "80".

    Edit: How much to torque the head bolts was the first question I asked on this forum. At that time the consensus was even and firm, tightening in a cross pattern, rather than a specific in/lbs. Since then, other posts have been made listing specific torques but I've just kept to palming the end of the socket wrench and tightening firm and even.
    Last edited by a moderator: Mar 12, 2008
  3. what tool did you use to tighten it?
  4. mickey

    mickey Guest

    A regular ratchet wrench with the end in my palm so that I can't get any leverage. Am I saying that in a way that makes sense?

    Edit: Buy some anti-seize stuff to use when you replace the cylinder stud. Its better for the aluminum block if you use it. Its next to the locktite in the stores. (if you're not familiar with the stuff)
    Last edited by a moderator: Mar 12, 2008
  5. not exactly. Mostly, Im worried about stripping the threads. So wouldnt a ratchet wrench grind the threads away?
  6. mickey

    mickey Guest

    Well, any wrench will strip the threads or pop the stud if you tighten down too hard. If I was using a box end wrench, I'd try to only turn it with one finger or something like that, without going all the way out to the end of the 'lever'.

    Edit: How about this for a image, the end that is in my palm is the ratchet end. So my lever is only half the width of my palm. Sort of. :grin:

    A search on headbolt + torque brought up this thread
    Last edited by a moderator: Mar 12, 2008
  7. but the heabolts have to be really tight or they wont stay in.
  8. mickey

    mickey Guest

    Fairly tight yes. Again, not so tight that they strip out. The block is aluminum of suspicious quality. Much worse if you strip the studs out of the block than if you just break a stud or strip the thread at the nut end.

    Did you actually strip the threads on the stud? That's odd. I would think that its easier to pop the stud in two than to strip the thread where the nut goes. Maybe you were crossthreading the nut. Can you post a picture of the damage?
    Last edited by a moderator: Mar 12, 2008
  9. mickey

    mickey Guest

    Maybe I misunderstood this question. Are you asking what I used to replace the stud? I took the cylinder off to allow some room and used the 2 nut technique. Put 2 nuts on the rod or stud and tighten them one against the other. then use one of the nuts to tighten or loosen the stud (the one whose turning would make it tighter against the other one. ie. Bottom nut to loosen, top nut to tighten.) That leaves the threads undamaged.

    Edit: I misspoke earlier, I just took the head off. There was no need to remove the whole cylinder.
    Last edited by a moderator: Mar 13, 2008
  10. Abeagle

    Abeagle Guest

    Last edited by a moderator: Mar 12, 2008
  11. thats genious!!! I stripped the top part of the rod where the top head nuts screw on because I tried to tighten one of the rods using the head nut. But thats very smart, the two nut thing. Im going to wait till the weather is a lot better before I start tweaking with my bike again. There are way too many things going wrong with it right now. Ill post some pictures hopefully tomorrow. Of the stud and the piston.

    till then gents...
  12. KanesKustoms

    KanesKustoms Member

    Did you get that head bolt ??

    FYI I have started making custom stainless steel engine studs
    They are much stronger than the studs in the engine Kits, and you can get them in the length you need. If this is something you can use let me know. Im not trying to make a buck here I will only charge for shipping and material cost.
  13. eltatertoto

    eltatertoto Guest

    hey, if its not stripped too bad, you could try re-threading it. just a thought.
  14. I haven't gotten to it yet, buisness has been really busy lately. But Ill get on it soon. Thanks for the offer, I might take it up, but do you mean the studs for frame mounting, or just the ones that hold the head onto the engine, the one that I stripped?
  15. KanesKustoms

    KanesKustoms Member

    I can make any length M6 1.00 thread pitch
    Just let me know the length you need
  16. BoltsMissing

    BoltsMissing Active Member

    If you have never tightened head bolts before on a engine, my advise would be to actually tighten correctly with a tourque wrench first so you get to know the "feel" of ft/lbs.
    If you say you have stripped the threads on a HT, it shows some have not progressed to that point of ever having used a torque wrench.
    You'll be surprised that 15/20 ft/lbs on the HT head bolts may not seem tight as you think, no where near that tight to strip a thread.

    I read somewhere here to, that it's not wise to use those dome shaped nuts as head bolts, because it's been known to screw up into the end of a closed off thread, and this will then turn the entire stud that holds the cylinder.
    Use some other nuts to tourque the head and if enough space, use the domes last.

    One other thing that is not mentioned,
    when re-tightening the head bolts, it's probably best to loosen 1/4 turn so the "crack" of a stuck nut does not crack on the tightening side. Crack the nut on the loosening, or loosen right off, one at a time, spray some CRC between the bottom of the nut and the top of the alloy head where the nut sits.
    Then re-tighten.
  17. wildemere

    wildemere Member

    Actual "clamping force" or "pull down" varies greatly with:-

    1 No lube on threaded parts

    2 Kerosene or similar

    3 Grease or good oil.

    The clamping force difference between 1 through 3 can be over 50% when using the axial measurement from a torque wrench.

    With rough or low quality parts the differences could be even greater.

    In a dry state up to 90% of torque can be consumed by friction on the flanges and threads.

    When lubricated this value decreases greatly.

    There is much to know about the subject of force measurement, bolt tension ect.

    Some manufacturers don't give torque values for fasteners but values in microns for the part pull down.
  18. mickey

    mickey Guest

    So, is recommended torque based on bone dry threads? I always wipe my threads with cloth but don't go to the trouble of using solvent or the like. Should I?
  19. BoltsMissing

    BoltsMissing Active Member

    OK, this one may need to start from scratch.
    Head studs and head bolts.
    Engine expirience from cars.

    Back when cars had caburtetors, in Australia, was the faithfull
    "Red Motor".
    These motors were often stripped and "done up".
    The head bolts, go into the engine block and some go into the water jacket.
    The recomnended sealant is called "Stag", it's brown/red in color and has a distinct odour about it.
    One had to smear the threads with Stag, then tighten up the head.
    When the car was initially started, it did not leave the workshop until the head was re-tensioned as soon as the water warmed up and ran for 20 minutes or so.
    This was so everything had dried up, "settled" and during that warm up the timing and some carby adjustments were done so it's ready for the next run after the initial warm up.

    After initial warm up of a HT, re-tension cos that lube/oil/kero-whatever would have dried up, caused some space, therefore a re-tension is warranted.

    if lets say an engine has been running for a month,by that time those head bolts have sealed firmly, "rusted" in, so if you try to undo them, they sound a "crack".
    If one has this "crack" sound when they are tensioning the head, then you do risk breaking the bolts or stripping a thread.
    Like I said before, loosen first, then re-tighten.
    Warm it up, then check the tension again, but don't loosen the 2nd time.

    To "visualize" what happens when you re-tighten a cylinder head in sequence, think of ironing a trouser leg, <<<>middle out->>>>>>|.
    Same with a head, tension it outwards.
  20. wildemere

    wildemere Member

    Who knows with these Chinese motors.

    Would have to know what the design engineers had in mind when specifying the number 12.

    Honda or BMW ect would be more specific.

    I would use oil or grease though.