Not always true, I have fixed the tranny on my old bike along the road several times. Once I broke a tooth off 5th gear and the tranny jammed. I had enough tools in my bag to take it apart,I got the broken tooth out and the tranny shifted OK. I spent the rest of the day riding it but only used 1st through 4th. This was a 72 triumph that I still own. Another time a tab washer that had been reused 1 too many times broke and let the main shaft in my 66 Triumph move back and forth. Once again I had the tools ion my bag to fix it enough to get me through the rest of the day. Fixed many broken chains along the road, mine once and other friends many times and was able to finish out the day. With my old bikes I also carried my timing tools with spare breaker plate and points already on it, extra set of plugs etc.... As long as it could be fixed without parts I was able to fix it so I do think carrying tools is a good idea.
Chain repair tools, extra plugs and plug socket, minimal socket set, something for the axle nuts etc.. Go over the bike and put together the tools you may need and spare gas line too along with some electrical tape and duct tape and a few zipties. I used to wrap a little of each tape around an old pencil to save room. Water pump pliers, wire cutters, chain breaker and master links (2) Tools to take off the gas tank, screw drivers, even a small compressor or pressureized cans to inflate a tire and tire plugs for tubeless tires. A rag and waterless hand cleaner. This is all stuff that just pops in my head I'm sure if I was putting a kit together I would add a couple things.
