Pheur...what he said. My bike has 40,000 kms on it. When I first got it I thought it ran like ****. It really starts to smooth out after it's broken in. Gets better all the way to about 5000 kms.

 

my motor on the street bob vibrates more at lower rpms . i cant really call it a vibration though , the motor just shakes in the mounts till i get it up around 2.5 or 3k after that its as smooth as glass. I did notice that when I changed pipes that it shook more at the lower rpms but since the stock pipes weigh about 3 times more than the bubs I expected to be able to feel the motor more. Honestly I think the stock pipes weigh 40 LBS. I have never felt any kind of vibration above 45 mph or so. it gets smoother the faster I go. I hope you figure out why your bike is doing this. Mine has never done anything like that ever.

 

Try reading the threads regarding motor mount shims.. some folks complained of the same issue and after shimming their enging mounts discovers the rattle, vibration issue to be no longer a problem.

 

I Know this is an old thread, but my '06 Super Glide does that same thing. It has 14k miles on it and the vibration has always been around 65mph (110kph) in 6 gear for me. That was until I installed an AME 9 degree rake kit. Then my vibration range changed! Now, I get a vibration at 50mph (85 kph) in 5 gear, and another at 60mph (100 kph) in 6 gear.

When I looked down at the forks while getting the vibration, my front tire was vibrating up and down, very fast at both those speeds. When the vibration ended or smoothed out, the tire stopped moving as well. I always thought this vibration had something to do with the front forks, as the engine always vibrated the entire bike, but smoothed out at higher RPMs. Maybe, on mine, the engine vibration at those RPM ranges is causing the front of the bike to shake, thus vibrating the front forks, and in turn causing the vibration to be felt throughout the bike. Worth a thought?

 

Sweet spot on my dyna is just above 2400 rpm, below that the pegs try to shake your feet off. There is also a "just off idle" sweet spot for boulevard cruising at low speeds with very low load I find. 60 kph in fourth gear is a really soft rumble with no shake. I don't put load on the motor at that rpm, but it sounds like its nice and relaxed and feels at ease.