I know a lot of people have wondered why a lot of shops won't touch older bikes; some comments/criticisms have been valid but my recent experience leads me to now defend the dealers in many cases. Some background...
I have a normal 9-5 shirt and tie job but I also do mc service work out of my home garage on some nights and weekends; I have a good setup with a real lift (1,500 lb. capacity), large compressor and a full set of mc-specific tools. I also have a friend who opened a multi-line dealership a year ago; He asked me to help out on weekends when I have time so I go in and do state inspections, oil changes, tire changing/balancing, general repairs, etc.
This shop started out accepting all bikes regardless of age/condition but they are already tightening up that policy, for several reasons. Here are some real-world examples of what they have experienced....
A 1940s era BMW that came in to the shop in November; They figured it would be a good way to fill some slow winter months shop time. It's still tying up a lift today as it sits disassembled and waiting on fruitless parts searches. The tech says he has countless hours online searching for parts; hours he can't charge the owner so the bike is a huge loss for the shop. First and last extensive "restore" they will take on...
Three "vintage" bikes sit out in the bullpen; all three are "abandoned by owner" because the shop agreed to work on them. After the techs spent a lot of time working on them the owners decided the bikes weren't worth the repair costs and stiffed the shop on the bills. More big losses.
Even when the customers are willing to pay for the shop time, it's still a major hassle for a shop to tear apart an old bike, find the problem, then not be able to get the part(s) needed; they can't have a lift tied up for days or weeks on end with a torn down bike while the tech scours ebay looking for used parts and waiting for auctions to end to see if they got the winning bid. They had that scenario recently on a KZ440 that had critical and unavailable carb pieces missing (thanks to someone previously "rebuilding" the carbs themselves and leaving pieces out). Another time black hole for the tech and shop...
Another reason new vehicle shops generally don't want to service old bikes with lots of problems (especially bikes that have been butchered to death by the owner or someone else and now want the shop to sort out their wiring bird's nest , messed-up carbs etc.): It is unfair to the other customers. Shops are very busy at times and it isn't fair to tell 5 or 6 other customers that we can't change their oil or mount and balance their new tires or inspect their bikes or install their fork seals, etc. today because one tech will be tied up all 8 hours trying to figure out one person's complete mechanical mess. New vehicle dealers organically create many service customers simply by selling them bikes; the dealer's first responsibility has to be taking care of these customers first.
My friend started out with the intention of cheerfully servicing everything on 2 wheels but reality has hit home; there is only so much shop time available and it must be allocated efficiently. That's not to say they won't do clearly defined service on older bikes, such as fork seals, oil and filter, tuneups, etc., but I now understand why a lot of shops (especially new vehicle dealerships) avoid extensive "vintage" work, especially during the busy season. Just my observations...