Established around 19481, motorcycle production began in 1952 with 44cc cyclomoteurs in several similar models including Kid-Master, Master, Standard and Populaire.
The Motobloc company name changed to Riva Sport Industries around 1955, the machines being marketed under that brand thereafter. In the UK 1956 models appeared under the name RSI-Motobloc.
In 1951-52 they sold the Swiss AMI 98cc scooter as the Ami Motobloc. The Sulky scooter was introduced in 1953 under the Motobloc marque and was further developed with RSI.
The motobloc.org site displays images of the RSI Motobloc mopeds without further comment, and a book by Jean-Luc Fournier on Motobloc autos shows the 1950s scooter prominently.
1952 BM 125 125cm3 Aubier-Dunne
1953 M 100
1953 BM 125
1953 M2S Aubier-Dunne 125 cc
1953 M4GL AMC 125 cc
1954 M4GL AMC 125 cc
1954 M4L 125cm3 AMC
1954 M475 AMC 175 cc (RSI)
1955 S65 65cm3
Motobloc Engine Types include:
Type B, 38cc
Type H, 44cc 38x38mm
Type 50, 49.9 cc
Type 244, 44cc
Motobloc of Bordeaux 1902 to 1931. Famous French automobile manufacturer, with no apparent relationship to the later Vichy firm.
nationalmotorcyclemuseum.co.uk has the following entry: Motobloc Engines 1955 to 1965 Inst. Manual for motorized cycles with Motobloc engine type 50 & gurtner C12 carburetter.
Sources: Cycle Memory, Amis Terriens, et al.