Couldn't find a simple answer. Can someone enlighten me?

Discussion in 'General Questions' started by Hello Moto!, Mar 22, 2016.

  1. Hello Moto!

    Hello Moto! Active Member

    I looked for a straight forward answer to a pretty simple question but was having trouble finding one.

    I would just like to know how tight should I torque the head bolts on my 66cc engine?

    I've heard 12 and also 15 on the torque wrench but not sure what is optimal? Honestly I got to 12 and became fearful that I was gonna strip something out so I stopped. Any suggestions?

    I just gained access to the forum and this is my first post outside of the introduction. So thanks again for access and I look forward to being a part of this forum!
     

  2. skyash

    skyash Active Member

    I herd 13. Then I did 15 works fine
     
  3. bluegoatwoods

    bluegoatwoods Well-Known Member

    When you say 12, 13, 15, I take it you're talking ft/lbs?

    That sounds like a bit too much. Particularly 15 ft/lbs. But 12 ft/lbs. sounds pretty high, too. I've been told to go with 120 inch/lb. Even that feels a bit too high to me. When I'm getting those bolts torqued in that range it feels like I'm close to stripping those threads.

    So I go with 110 inch/lb. I do it in two steps as well. I'll torque all four to about 70 inch/lb or so and then I'll torque all four the rest of the way.
     
  4. Hello Moto!

    Hello Moto! Active Member

    Yes I mean ft/lbs. Those are the only marks on my trusty torque wrench lol. How do you get from inch/lb to ft/lb? If I had an educated guess maybe you just divide by 12?

    Yes I must agree with you on the feeling of possibly stripping the threads up in that range. Like I said at 12 ft/lbs it felt like I was tempting fate so I stopped. It has been said that a wise man senses danger and turns back, a foolish man senses danger and keeps going lol.

    Anyways, Thanks.
     
  5. Hello Moto!

    Hello Moto! Active Member

    Thanks.
     
  6. bakaneko

    bakaneko Active Member

    you are right

    120 in/lb * (1ft/12 in) = 10 ft / lb
     
    Legwon likes this.
  7. crassius

    crassius Well-Known Member

    6mm stud = 6 to 8 ft/lb, 8mm stud = 10 to 12 ft/lb
     
    Legwon likes this.
  8. skyash

    skyash Active Member

    One day the studs felt like thay were spinning and thay come straight out the domed nuts head
     
  9. sbest

    sbest Active Member

    The weakest part is where the stud threads into the aluminum.
    So while 15ft/lbs is ok for the stud and nut, it will pull the threads out of the aluminum.
    This is a pretty good chart:
    [​IMG]
    Better if you lube your threads. Loctite is a lube too.
    There are a huge number of factors involved, but these are safe values.
    Steve
     
  10. frostic

    frostic New Member

    i go with 12 maximum... anything higher is not nessisarry at all and could cause issues with the soft aluminum head bolts stripping out...
     
  11. Hello Moto!

    Hello Moto! Active Member

    Thanks a lot for the responses. Glad I wasn't to far off at 12lbs. I'm havin a little issue with some leaking around the head. I'm gonna try to resurface it lightly as I noticed it has minor surface issues. I'm also going to make a new gasket and see if that helps. I found some useful information on the process browsing the forums and some decent youtube videos. Thanks again guys.
     
  12. HeadSmess

    HeadSmess Well-Known Member

    tight enough so they stay on but dont break?

    i dont bother with torque wrenches... 99% of the time.

    use teflon tape for the head gasket. i feel like i always say that...
    but seriously. teflon tape is the BEST material for head gaskets. just twist a length of it into a string and think a bit.

    yep, plain old white ptfe plumbers tape.
     
    Timbone likes this.
  13. butre

    butre Well-Known Member

    I honestly don't even own a torque wrench. when you've been messing with this stuff for more than a few years you can just feel what's right.

    the only times I've ever needed a torque wrench I just rented them.
     
  14. sully1617

    sully1617 Guest

    the paperwork i received with my gt5a says 10ft lbs. i'm sure you could tighten a little more but be careful these engines use cheap aluminum and strip easily
     
  15. KCvale

    KCvale Motorized Bicycle Vendor

    I buy Skyhawk kits, always turn the head around and usually paint it, and torque my heads in an X pattern 5# at a time to 20#.
    50 or so 2-stroke builds and never had a blown head gasket or broken bolt or stripped engine.
     
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