[elvo]

I've stumbled across this:

http://www.superbikeplanet.com/NSR500.htm


The particularly relevant bits:
"
Just as significantly, they also changed the direction of crankshaft rotation. Ever since '84 there had been dark mutterings about 'single-crank voodoo' and a growing belief that the crank's gyro effect was responsible for the bike's wayward handling. In other words, crankshaft inertia made it hard work to steer the bike from its current course. Yamaha ran contra-rotating cranks, which canceled out any gyro effect, HRC thought that was the reason the Yamaha handled better.
Two years later these suspicions would push HRC into testing their own twin-crank motor (not long for life, alas, for the single crank was now The Honda Way) but for now a change of rotation would have to do. Before '87 the NSR crank rotated anti-clockwise, so when the rider opened the throttle, the front would go light, sending the bike disastrously wide on corner exits."
"
There was another advantage to the Big Bang. Although reversing crank rotation in '87 had solved front-end lift, it hadn't totally exorcised single-crank voodoo.
As Doohan explains: "After they changed the rotation the bike would lift the rear when you accelerated, so you'd have the back tire spinning and the rear would lift, making the wheelspin worse. At the same time it pushed the front down, messing up the steering". The Big Bang eradicated the voodoo purely by chance, because the extra vibration produced by the close firing order required a counter-balance shaft that damped out the gyro effect."


It seems the smart boys at Honda Racing Corporation have gone through the same evolution as we have: motor spinning opposite of wheels : lots of wheelspin, front end being pushed down. Motor spinning in the same direction as wheels : poppa wheelie everywhere and you can really feel the gyro effects. Counterbalance shaft spinning opposite the motor was very successful because it was the happy medium ... .... until they figured out how to make the power of the engine suitable for the chassis and tyres. (I.e. less outright power with instant, smooth, predictable delivery and not too much engine braking)

There are power-loving maniacs out there who like the flywheel. I've learned to motor down and gear up ( = motor spins slower = less gyro effects), which in my opinion is the next step in the evolution.

What the article doesn't mention is that after each engine configuration change, suspension changes were needed. MotoGP boys tend to fiddle with swing arm length and position, we fiddle with camber links and anti-squat.