From ananna6969@gmail.com@21:1/5 to All on Sat Aug 17 16:59:18 2019
Look at the Chotia 460B, John Chotia had the same idea, to make his own engine in house for the Weedhopper/Woodhopper/Gypsy/etc. Unfortunatly, when he was killed and the company went under they threw the castings into some lake so nobody could restart
building the engine.
Also, in the back of "Berger Burr's Ultralight & Microlight Aircraft of the World 2nd Ed" is a whole encyclopedia section of old engines used in 80's era ultralights.... a good starting point for ideas.