of course, ballance the prop and spinner. I would not mess with the engine, as far as ballance goes. Let it shake. And by the way, the harleys cant be in one jug...the pistons do NOT fire at the same time, its one right after the other, and they do vibrate all the way through the rpm range, at different speed of vibration of course, and also not opposed like jap bikes. Why do you think the chicks like harleys sooooo much?! lol let it shake bro, let it shake. All single cylinder engines have a point where they shake more ......or less. My 90s vibrate at a little after idle, but smooth out just fine.
just my thoughts.
d