5 YAMAHA FZ750
In the maelstrom of mechanical marvels the manufacturers came out with in the 1980s, it would be easy to forget the significance ofyamaha’s 1985 FZ750. It wasn’t just the tech in the engine.the motor’s design also set a new benchmark for packaging.
Yamaha created the first four-valve combustion chamber in a mass-produced bike with the almost-forgottentx500 twin.the FZ750 went one better with five; three inlet and two exhaust. It would become ayamaha hallmark until a four-valve layout was adopted for the 2007YZF-R1 to meet emissions regs.the key claim for the five-valve design was that through having 10 per cent more inlet area than a four-valve combustion chamber, torque and power were increased through better cylinder filling. Being smaller and lighter the valves allowed the engine to rev higher too.another benefit was that valve springs could be lighter for fewer mechanical losses and the seats got an easier time too. Dished pistons allowed for an elliptical combustion chamber that gave more space around the spark plug than a four-valve pent roof combustion chamber.
The cylinder head was a clever two-part design.the top cam case is removed for valve shim changes while a lower case contains the combustion chambers and valves.
However it was the downdraught intake system, learned fromyamaha’s F1 engine experiences that was key.the carbs are mounted horizontally and the fuel/air mixture goes straight down to the combustion chambers – a real revolution.to accommodate this the block had to be angled forward. In doing soyamaha pushed the packaging boundaries.true mass centralisation was born.
“Yamaha pushed the packaging boundaries. True mass centralisation was born”
One hell of an engine, rest of it not bad either
Five valves per cylinder, and Yamaha experimented with seven – and even nine