Ive done one Zero. I dislike these threads because the bike purists tend to
beat you up. I have about 2000 miles on this one. Its a 25cc 4 cycle Subaru
(Robin) 1hp. Its a golden eagle. They are great folks to deal with.
I did this because I was recovering from broken collar bone. Take some pressure
of my shoulder. Its a super grocery getter.

Note I pedal this more than motor it now. As a rule I dont run it in town
and certainly not the MUP! And by all means dont disturb the serenity of
quiet neighborhoods in the evening. Its called RESPECT
Weighs 12 lbs (motor 6lb). 47 lb total w/bike.
It would be difficult pedaling a 100lb Moped! Rear rack is self made. Ive put
over 85lbs on this rack. With 70 lb load It will still do 27mph. 32 if you pedal.
Ive passed up some stunned roadies.

This little robin is work of art. Its clean as a whistle even after all the miles.
Easy starting with decompression. Torque curve on this motor is pretty much
a straight line. Meaning same tork at 4k rpm as 7500rpm. For a bike it perfect.
Its barely audible at idle. At speed its mopedish sound.. 240 mpg avg.
260mpg just putting along. As it sits with 17oz tank and 30oz bottle range is 85 miles.
Little over a penny a mile.

At any rate I like this setup. Efficiency is important for range and gas weighs 6 lbs gal.

FWIW Why would you want a hot motor between your ankles?

I can expound some more info but Im really not up to waxing philosophical of why
one shouldnt do this.