Torque steer.

[skippyc]

I had a R75/5 and it loved to react to acceleration. But the R65 doesn't react at all.
So What is the difference is it a lighter flywheel?

[Tony Smith]

In a word - yes. I notice it shifting between my 860 and the wife's R65/80. The heavy flywheel was fitted the the R80 engine to avoid having to also got a late model gearbox.

[georgesgiralt]

Hi Guys,
I'm very late on this, but the flywheel is only a very small part of the equation. (and for 1979 model, it is quite the same as on the /5... )
The main improvement where first the gearbox input with it's spring shock absorber. Then they put another one in the swing arm and that did the trick.
On the 1981 model, they lightened the clutch and added some smoothness to the ride.
I also own a Guzzi (V7-III, E4 model) and I miss the big spring in the swing arm a lot. The bike react violently at every bump, even with the most expensive shocks and a lot of tuning...