Saturn in Poland made a 25 HP, horizontally-opposed, 500 cc, twin-cylinder engine for ULM. It was built under the direction of J.Janowski. It was the 500B model.

From Appendix 10: See J. Janowski. Design of the 500 B engine for the “Spinner” J-1 motorsailer. It is built from, and with parts of the MZ motorcycle.

“Spinner J-1 with Saturn 500B engine” (PiP-SP)

-Polawsski and Rabiegi also participated in the construction of this engine. It is in the year 1969.

From Appendix 12: Saturn 500B engine, built by J. Janowski, plus two companions, to equip the J-1 “Spinner” ultralight. It gave 23/25 CV.

“Saturn 500B Engine” (PiP-SP)

-It clearly uses cylinders from the MZ motorcycle.