They were designed by Giulio Carcano who did the V8 and V twins. The top end is like the early V Twins turned 90 degrees. Everything you read about them talks about them being a cheap design, but not really cheap, it's just that they used die casting. A very overbuilt bottom end...although it has broken a crank. I've had it from new, it was off the road for many years and got it back on the road a few years ago. It's pretty rough, and off the road again...a broken fuel banjo.