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March 5, 2021

updated 2021-03

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Asso Pistons

ASSO Pistons

Asso Factory

ASSO Factory


ASSO pistons were made in Italy mostly for Italian mopeds. ASSO stands for Assoluta Sicurezza Sempre Ovunque (Absolute Security Any time Anywhere). Early pistons said only “ASSO”, while later 1980’s ones said “ASSO.W”. Somehow ASSO merged with or was acquired by a German name, maybe some “kolben werke” to become ASSO Werke.





1950’s to 1970’s
1. Morini S5K2
2. Min. V1 (1hp)
3. Sachs 504-1A

Why do Morini, Minarelli and Sachs pistons have the same dimensions?

Connection: Erio Testi worked in his father’s bicycle factory until 1953, when he was sent to Austria, at Fichtel and Sachs, to learn about small two stroke engines. After Testi returned, he transferred the two stroke engine knowledge to his friend Vittorio Minarelli, who was partners with Franco Morini at Fabricca Bologna Minarelli FBM. The two Italian engineers used many of German engineer Ernst Sachs production methods and knowledge, like casting and metallurgy, and design principles, like bore and stroke, port timing, sizes and thicknesses, geometry, etc. Later FBM split into Motori Morini Franco and Motori Minarelli. That’s why early Sachs, Morini, and Minarelli pistons share the same design!