I take my D700 & D300 on both my bikes all the time and have experienced no issues at all. I have a 2005 HD Fatboy with leather saddlebags and I usually place my cameras inside wrapped in several microfiber rags. My D700 almost always has my 24-70 on it.
I also have a Touratech bag that I attach to the rear seat of my 2006 BMW K1200GT that I frequently ride out to Death Valley, Utah, Grand Canyon, and last month, up to Yosemite National Park. The bag simply zips to a base that attaches to the rear seat. I take it inside when I get off the bike for lunch or a restroom stop.
I think if you take care securing your gear and protecting it from other items, you should have no problems.
I have always carried mine on my Dynaglide inside the saddlebag and wrapped with a towel. No problem ever.
However, it was not possible to get to the camera as I was riding so I solved that problem this year. I bought a product called a Spider Holster. Pictured below is the Spider Plate that attaches to the camera. You will notice the plate has a built in wrench holder for the allen wrench. It works well! The next pic shows my D700 hanging by my side. This fine product allows you to carry the camera safely anywhere you want to go.
It has a ball pin that fits into the Holster and there is a safety catch so the camera cannot fall out. Yet you can 'draw' the camera up for use about as quick as you could pull a gun out of your waistband, as shown in the last pic taken as I rolled through the Texas Hill Country.
This way, if I stop for gas and go in to get something to eat or whatever, the camera stays with me. I do still carry that towel though in case I run into a rainstorm. Then the camera goes into the saddlebag wrapped in the towel. The Spider Holster with the plate and belt sells for $112 and is the best way to carry a camera in my opinion. I have no connection with this company other than owning the product. Perry
Jim, I believe you are going to love the Spider Holster. I list it as the most favored photography accessory item I own. It is very well made and the company has customer service that will surprise you. Tell us how you like it (or dislike it), after you have used it a while. Perry
I am not so sure I can agree with you guys on the BSA singles and vibration. I owned and rode three different BSA Gold Stars (500cc single) along with a B-33. They were very smooth machines. These were pre-Victor models but similar machines non the less. Kicking the Gold Star was sometimes a challenge, but if you had the bike in tune as it should be and used the spark retard it would start easily. Perry