Found an interesting article about the 1939 500cc Gilera with the Rondine four-cylinder engine. These bikes were raced and won TT races well into the 60's. They had double-over-head camshafts, forced-inducting supercharger and was water-cooled, producing 60 kW (80 hp) @9000 and had a top speed of 140 mph. Wow, that is similar specs to the the Z1-900 from 34 years later. Albeit, with a supercharger. But these were 500 cc, not 900 cc like the Z's. Blows my mind that they had all that technology even back in 1939, which is so common now. What is also amazing is this engine was designed in 1923.
Nice bike Joe
All those specs and more in 1939
Rolls Merlin comes to mind
Someone just needs to decide to just use the technology of the time
SEND PM WITH BOTM NOMINATIONS
Original owner 78 1000 LTD
Mr Turbo Race Kit, MTC 1075 Turbo pistons by PitStopPerformance , Falicon Ultra Lite Super Crank, APE everything. Les Holt @ PDM's Billet Goodies . Frame by Chuck Kurzawa @ Logghe Chassis . Deep sump 5qt oil pan. RIP Bill Hahn
Yes, the engine itself was developed in 1923. I think think in this case, according to the article, the innovation was using this engine in a side to side configuration in a motorcycle instead of longitudinally which had been done before. Gave better handling stability and avoided the inherent over heating of the back cylinders. I think what the Japanese contributed to the motorcycling world was a transverse in-line four that used technology that someone else had innovated (like the Gilera), but made it cheaper and reliable for the masses. The Gilera was a racing bike. As we all know, there were many other manufactures with four (Brough Superior Austin Four), six and eight cylinder engines produced. Not sure how practical a six or eight cylinder motorcycle wold have been for the time. But I would think a four cylinder should have seemed reasonable. I suspect the cost along with the lack of frame , brake and tire technology was probably a factor in four cylinders not gaining traction with the public until the Japanese bikes came out. The first double overhead cam four valve per cylinder engine was introduced by Peugeot in a Grand Prix car in 1912..And that is still not so common. Interesting article.