Enzo Simonini, formerly of Fiat, began tuning two-stroke engines for off-road machines in the early 1960s, and then sold conversion kits which were well received in Italy, concurrently developing machines for other manufacturers.
He built his first Simonini 50cc motorcycle using his own frame and a tuned Sachs engine in 1971, and this was followed in 1972 by 125cc 5 and 6 speed models, Sachs-powered.
Kreidler 50 engines were introduced in 1974, and that year his own 125 and 250cc engines began development.
A partnership was formed with Franco Fornetti and the business flourished for several years with reasonable competition success. There was a disagreement between Fornetti and Enzo, and as a result Enzo Simonelli left the firm. Things slowed down in the early 1980s, and production ended in 1983.
Simonelli supplied handsome sports mopeds to AJW of Great Britain in 1976.
Sources: motoclubstoricoconti.it, IceniCam