I have never been on the Autobahn, but the streets of San Diego seem to be
thought of as a great second with all the kids trashing their cars over
here.
But back to driving your 600 at 65+, I do it all the time. And as to top
speed, all the Honda 600's I have driven seem to go over the
distributor-point threshold at about 75 mph or at about 7K rpm. Then they
seem to lose power and drop off to around 6K rpm and start up again. The
lobes on the advancer assembly and the points can only go so far and they
mechanically will not allow more rpm. The only 600's I have seen with
greater speedometer speed were ones that had a Constant transmission
Speedometer gear in a synchro transmission. It makes the speedometer go
faster. But the 45hp versions, I understand were able to attain greater
speeds. I attached the Power Curve illustration from the Honda 600 Factory
manual. If you look at the performance curve it peaks at roughly 6500 rpm
and falls off sharply as it reaches 7000 rpm.
Bill