Vintage Whizzer Engines Had More Low-end Torque?

Discussion in 'Whizzer Motorized Bicycles' started by Hal the Elder, Nov 7, 2008.

  1. Hal the Elder

    Hal the Elder Member


    In an earlier post you mentioned that Vintage Whizzer engines had more low-end torque than today's NE engines.

    Was this due to higher compression or a longer stroke?

    Those engines would probably not qualify for today's "under 2HP" licensing criteria.


  2. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Hal, There are many differences that change the torque curve, but one of the major differences was the flywheel. The vintage motor had a lot of "flywheel action", because of the thinner, taller, and heavier flywheel. The bore and stroke on the original [vintage] was 2.25" X 2.125" or 8.449 C.I. [138.457 CC], whereas the new version is 57 MM X 54 MM or 137.795 CC. The original motor had a slightly larger piston .15", and a slightly shorter stroke .025". You will most likely see the new edition motors advertized in size from 123 CC to 148 CC, but they are all really 137.795 CC [138 CC]. The compression ratio was certainly higher on the original motors, and all of the heads were a much better design. The original "H" & "J" motors were rated at 2.5 HP, and the later "300", "300S", "500", "600S", and "700" motors were rated at 3 HP. Of course with more power came more heat, and the vintage company simply installed a Hi-Fin head to lower the operating tempature. It didn't take me long to notice my new edition motors produced very high operation tempatures when I increased the power. And since I didn't want to ignore the problem or re-invent the wheel, I contracted several companies in the mid-west and simply had them make a Hi-Fin head to fit the current motor[problem solved].

    I am not sure, but maybe the originals could be "antique status". The original motors were often advertized as 2.5 brake HP, which might be a different rating, maybe not. Maybe you could get a poor running "H" motor to test under 2 HP, LOL.

    Have fun,
  3. Hal the Elder

    Hal the Elder Member

    Flywheel Discussion:


    When an engine is running at speed, the load can borrrow from the flywheel's stored energy, but once that stored energy is used, extra energy from the engine is required to replace it. It isn't always there to tap.

    From a standing start, an engine has to accelerate not only the dead weight of bike and rider, but it must also store energy in its flywheel, which would tend to make it have less low-end torque than an engine with a light flywheel. But then again, a flywheel will ADD its stored torque to that which the engine is producing at any time.

    It must have been the higher compression of the Vintage engines that gave them more torque.

    Many hotrodders have their flywheels "chopped" to reduce the inertia that must be overcome during acceleration.

    Other things which are analogous to a flywheel in terms of storing energy are:

    A Compressed Spring

    A Tank Of Compressed Air

    A Charged Capacitor

    A Suspended Weight

    I have always admired flywheels. You get back from them what you put into them!

    Last edited: Nov 9, 2008