I have to agree with all of the above experiences.
When my $80.00 1650 came home from the auction, it was so smooth running
I thought it was a opposed twin.
Upon further inspection it had 1 loose bolt holding the pan to the iso rail.
The engine sat there merrily jumping around but transmitting no vibration to chassis.
It was like it was setting on a huge soft cushion.
Wished it was that smooth after I repaired everything.
Let the new mounts wear in and it will get better somewhat but it will never be like a twin of any kind.
And as others have said do take the hood hinge pin out and mash/squeeze the hinge to bring it back tight, point the pin and drive it back in/and install.
then tighten everything that rattles, one item at a time.
I was lucky inasmuch my iso's were original and good shape.
14-16 hp engines by nature being a big single, vibrate
Hell, when I was a young man, it cost $.25 to get a bed to vibrate like that in a motel room, and another $.25 to listen to a radio ( no TV then) Ha,LOL!