Nut Sizes on Cylinder Head

Discussion in 'Motorized Bicycle Welding, Fabrication and Paintin' started by madwheels37, Feb 25, 2011.

  1. madwheels37

    madwheels37 New Member

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    Could someone tell me what size the nuts are on a cylinder head for a 2stroke 49 and 66cc? What type of socket will I need? Cause I can't seem to find one that will fit between the fins. Thanks.
     
  2. earl.k

    earl.k New Member

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    i have two shyhawk motors.. and they both have different size nuts on the head bolts.. either way i never have a hard time getting a socket wrench between the fins???

    on my one motor, the size is 13mm.. and the other one has 10mm. and both are easy to get at with a socket wrench.
     
    #2 earl.k, Feb 25, 2011
    Last edited: Feb 25, 2011
  3. max350

    max350 Member

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    nuts 13mm = M8

    nuts 10mm = M6
     
  4. dmb

    dmb Active Member

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    DON'T FORGET if acorn nuts bottom out you run a chance stripping the studs out of the motor case!
     
  5. earl.k

    earl.k New Member

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    most are sizes right, but good point. one of my kits came with two washers and a lock nut washer under all my head bolts.. and im thinking its because the acorn nuts bottomed out.
     
  6. 2door

    2door Moderator
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    Acorn nuts can and will bottom out. I replace them with shouldered hex nuts for that reason. In fact I would say that most of the factory installed acorn nuts are too shallow for the purpose. What happens is the nut bottoms out then there isn't enough thread on lower end of the stud to properly tighten down the cylinder head. I've found too many to discount this as just a rare occurance. The acorns are pretty and make for a nice look but they are unreliable as a proper cylinder head fastener.
    Here's an old thread that talks about this subject> http://motorbicycling.com/f3/acorn-vs-hex-nuts-6846.html
    Tom
     
    #6 2door, Mar 18, 2011
    Last edited: Mar 18, 2011
  7. Goat Herder

    Goat Herder Gutter Rider

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    [​IMG]

    I have been using lock washers like this with fair success.
     
  8. dmb

    dmb Active Member

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    i use flange nuts cause i got lots of metric stuff yrs ago, dont use nyloc to torque but you guys know that. dennis
     

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