current single cylinder technology and ignition design-produces singles which are glass smooth in actual operation.
My new models -even a 10 lb Funtana equipped with a 25cc single, also my 23 lb EXTRA with 80 single - do not shake-at idle or thru acceleration .
Theory and old info on single cyl unbalance is well known
Some single do shake - and 4 stroke glow engines of large displacement and high compression are among the worst - timing is simply a result of heat/pressure /fuel.
Gasoline setups with well designed and tailored ignition curves ,do wonders for the vibration problem and virtually eliminate the classic 2500-3500 rpm shake or the rough idle.

And now - back to the movie-------------where we find Stanley saying to Oliver ---