The last time I had the motor running, it howled when I got to 2500 or 3000 rpm. This week, I set everything up and reproduced the problem. It still howls, and the speeds are 2600 and 3100. No video shot for the 'before' due to technical difficulties ... the phone ran out of memory and did not save the video.
To fix this howling, I set the transmission and motor back to vertical, ran the motor at a few hundred rpm, engaged and disengaged the clutch a few times and allowed it to center again. The video again ran out of space in the phone and did not save.
After putting all of the oil back into the transmission - it drains out when the transmission is put vertical - I went through the phone to check the 3000 rpm video to make sure I knew the howling speeds. That's when I found out the videos were not saved ... SIGH!
After clearing out some old video on the phone, we were good to go! The video shows the results - no vibration in the 2600 and 3100 rpm ranges. There is a bit of a howl that you can hear on the video, and the motor is by no means quiet. But it's not going to vibrate itself apart.
I did separate audio for this run, using a bluetooth headset and a separate phone. Want to guess what went wrong? I ran out of space on my old phone! I don't appear to learn very quickly ...
The lack of separate audio for a voice-over is why I sub-titled the speeds.