S p e c s:

1951 - 1952
Made under license in France
engine: single cylinder, air cooled 2-stroke
induction: piston ported
bore: 56.6 mm
stroke: 49.8 mm
cubic capacity: 123.67 cc
compression ratio: 6.3: 1
bhp at rpm: 4 @ 4,500
lubrication: 5% oil
transmission: 3 speed constant mesh
primary drive: 22/69
1st gear: 12: 1
2nd gear: 7.5: 1
3rd gear: 4.78: 1
clutch: wet - 2 cork plates
carburetor: Guertner R.N.V.17
venturi diameter: 22mm
barrel manifold: 17mm
main jet: 31
idle jet: 40/100
throttle slide: No. 11
ignition: contact breaker & coil
ignition timing: 28 degrees BTDC
breaker gap: 0.3 - 0.5 mm
voltage: 6 volt AC
battery: n/a
wheels: 8"
tires: 3.50 x 8"
top speed: 43 mph / 70 kph
 

Note: ACMA produced Vespas from 1951 to 1962 in Fourchambault, near Dijon, France. Some interesting features of the 1951-52 model were:
  • The fan cover is visible through a cut out in the motor side cowl.
  • A special exhaust w/two pipes
  • Available in silver (with a bit of green) in '51
  • Available in dark metallic green in '52
  • 8" wheels
  • A trapezoidal rear light
  • The pressed steel headlamp assembly is bolted to the handlebar.
  • X style rear rack

Although they look very similar, there are some small differences between the 1951-52 ACMA 125 and the later model which are listed on the ACMA 125 1953-54 page.

The engine is very similar to the 1950-52 Italian Vespa 125 and many parts should be interchangeable.

Thanks to Jean-François Bourque for the info and Oliver Montuori from Urbanscootershop in Nice, France for the image.