head bolts

Discussion in 'Whizzer Motorized Bicycles' started by ohio frank, Jan 8, 2010.

  1. ohio frank

    ohio frank New Member

    i was wondering why the allen bolts are used for securing the head. the old harley davidson motors used a similiar set up. when harley wanted to make their motors more reliable they starting using studs with nuts and washers. no more blown head gaskets, stripped holes, etc. i am making studs for my motor and i will post my results.

  2. Studs!!!

    I can tell you it works great to use studs. Make them from grade 8 or from allen bolts with the heads cut off. It is difficult to find bolts that are fully threaded but they are out there. I did this right out of the gate , never have had any stripped threads to deal with., its been 8 years now so it works!
    Best of luck
  3. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi ohio frank,

    The early Whizzer "H" motor used 1/4" bolts and they soon upgraded to 5/16" bolts to solve issues with blowing head gaskets. The new edition motors used 6 MM allen bolts, however the NE motors upgraded to 8 MM allen bolts and reduced head gasket issues.

    On WC-1 motors [1999 to 2004] I converted several to 6 MM studs. The main advantages to studs are the complete use of every thread in the aluminum cylinder, use of high temp Loctite, and the stress is transferred to the nut as opposed to the cylinder threads.

    On a couple of the WC-1 motors I upgraded to the larger bolts, but considering the short life of most WC-1 cylinders, I just stopped wasting my time and converted to the NE cylinder [with larger head bolts].

    Almost 99% of the time the 3 rear headbolts are the problem and is caused by exessive head and shorter cylinder threads [must miss the intake and exhaust ports].

    Keep us posted on your progress.

    Have fun,